flagellate (adj.) Look up flagellate at Dictionary.com
1851, from flagellum + -ate (1).
flagellation (n.) Look up flagellation at Dictionary.com
early 15c., "the scourging of Christ," from Old French flagellacion "scourging, flogging," or directly from Latin flagellationem (nominative flagellatio) "a scourging," noun of action from past participle stem of flagellare "to scourge, lash" (see flagellum). In a general sense from 1520s.
flagellum (n.) Look up flagellum at Dictionary.com
"long, lash-like appendage," 1837, from Latin flagellum "whip, scourge," also figurative, diminutive of flagrum "a whip," from PIE root *bhlag- "to strike" (cognates: Latin flagitium "shameful act, passionate deed, disgraceful thing," flagitare "to demand importunately;" Old Norse blakra "to flutter with the wings," blekkja "to impose upon;" Lithuanian blaškau "to and fro").
flageolet (n.) Look up flageolet at Dictionary.com
flute-like instrument, 1650s, from French flageolet, diminutive of Old French flajol, from Provençal flajol, which is of unknown origin.
flagitious (adj.) Look up flagitious at Dictionary.com
"shamefully wicked, criminal," late 14c., from Old French flagicieus or directly from Latin flagitiosus "shameful, disgraceful, infamous," from flagitium "shameful act, passionate deed, disgraceful thing," related to flagrum "a whip, scourge, lash," and flagitare "to demand importunately," all from PIE root *bhlag- "to strike" (see flagellum). Related: Flagitiously; flagitiousness.
flagman (n.) Look up flagman at Dictionary.com
also flag-man, "signaler," 1832, from flag (n.1) + man (n.). Earlier it meant "admiral" (1660s).
flagon (n.) Look up flagon at Dictionary.com
"large bottle for wine or liquor," mid-15c., from Middle French flacon, Old French flascon "small bottle, flask" (14c.), from Late Latin flasconem (nominative flasco) "bottle" (see flask).
flagpole (n.) Look up flagpole at Dictionary.com
also flag-pole, 1782, from flag (n.1) + pole (n.1). Flagpole-sitting as a craze is attested from 1927.
flagrance (n.) Look up flagrance at Dictionary.com
"glaring shamefulness," 1610s, from French flagrance or directly from Latin flagrantia "a glow, ardor, a burning desire," noun of quality from flagrantem "burning, blazing, glowing" (see flagrant). Related: Flagrancy (1590s).
flagrant (adj.) Look up flagrant at Dictionary.com
c. 1500, "resplendent" (obsolete), from Latin flagrantem (nominative flagrans) "burning, blazing, glowing," figuratively "glowing with passion, eager, vehement," present participle of flagrare "to burn, blaze, glow" from Proto-Italic *flagro- "burning" (cognates: Oscan flagio-, an epithet of Iuppiter), corresponding to PIE *bhleg-ro-, from *bhleg- "to shine, flash, burn" (cognates: Greek phlegein "to burn, scorch," Latin fulgere "to shine"), from root *bhel- (1) "to shine, flash, burn" (see bleach (v.)). Sense of "glaringly offensive, scandalous" (rarely used of persons) first recorded 1706, probably from common legalese phrase flagrante delicto "while the crime is being committed, red-handed," literally "with the crime still blazing." Related: Flagrantly.
flagship (n.) Look up flagship at Dictionary.com
also flag-ship, 1670s, a warship bearing the flag of an admiral, vice-admiral, or rear-admiral, from flag (n.) + ship (n.). Properly, at sea, a flag is the banner by which an admiral is distinguished from the other ships in his squadron, other banners being ensigns, pendants, standards, etc. Figurative use by 1933.
flagstaff (n.) Look up flagstaff at Dictionary.com
1610s, from flag (n.) + staff (n.). The settlement in Arizona, U.S., said to have been so called for a July 4, 1876, celebration in which a large flag was flown from a tall tree.
flagstone (n.) Look up flagstone at Dictionary.com
"any rock which splits easily into flags," 1730, from flag (n.2) "flat, split stone" + stone (n.).
Flaherty Look up Flaherty at Dictionary.com
surname, Irish Flaithbheartach, literally "Bright-Ruler."
flail (n.) Look up flail at Dictionary.com
implement for threshing grain, c. 1100, perhaps from an unrecorded Old English *flegel, which, if it existed, probably is from West Germanic *flagil (cognates: Middle Dutch and Low German vlegel, Old High German flegel, German flegel), a West Germanic borrowing of Late Latin flagellum "winnowing tool, flail," in classical Latin "a whip" (see flagellum).
flail (v.) Look up flail at Dictionary.com
mid-15c., "to whip, scourge," from flail (n.). Sense of "to move like a flail" is from 1873. Related: Flailed; flailing.
flair (n.) Look up flair at Dictionary.com
mid-14c., "an odor," from Old French flaire "odor or scent," especially in hunting, "fragrance, sense of smell," from flairier "to give off an odor; stink; smell sweetly" (Modern French flairer), from Vulgar Latin *flagrare, dissimilated from Latin fragrare "emit (a sweet) odor" (see fragrant). Sense of "special aptitude" is American English, 1925, probably from hunting and the notion of a hound's ability to track scent.
flak (n.) Look up flak at Dictionary.com
1938, "anti-aircraft gun," from German Flak, condensed from Fliegerabwehrkanone, literally "pilot warding-off cannon." Sense of "anti-aircraft fire" is from 1940; metaphoric sense of "criticism" is c. 1963 in American English. Flak jacket is by 1956.
flake (n.) Look up flake at Dictionary.com
"thin, flat piece of snow; a particle," early 14c., also flauke, flagge, which is of uncertain origin, possibly from Old English *flacca "flakes of snow," or from cognate Old Norse flak "loose or torn piece" (related to Old Norse fla "to skin;" see flay); or perhaps from Proto-Germanic *flago- (cognates: Middle Dutch vlac, Dutch vlak "flat, level," Middle High German vlach, German Flocke "flake"); from PIE *plak- (1) "to be flat" (see placenta). From late 14c. as "a speck, a spot."
flake (v.) Look up flake at Dictionary.com
early 15c., flaken, (of snow) "to fall in flakes," from flake (n.). Transitive meaning "break or peel off in flakes" is from 1620s; intransitive sense of "to come off in flakes" is from 1759. . Related: Flaked; flaking.
flaky (adj.) Look up flaky at Dictionary.com
1570s, "consisting of flakes," from flake + -y (2). Meaning "eccentric, crazy" first recorded 1959, said to be American English baseball slang, but probably from earlier druggie slang flake "cocaine" (1920s). Flake (n.) "eccentric person" is a 1968 back-formation from it. Related: Flakiness.
The term 'flake' needs explanation. It's an insider's word, used throughout baseball, usually as an adjective; someone is considered 'flaky.' It does not mean anything so crude as 'crazy,' but it's well beyond 'screwball' and far off to the side of 'eccentric.' ["New York Times," April 26, 1964]
flam (n.) Look up flam at Dictionary.com
1630s, "sham story, fabrication," also as a verb, "to deceive by flattery;" see flim-flam.
flambe (adj.) Look up flambe at Dictionary.com
1869, of certain types of porcelain, 1914 as a term in cookery, from French flambé, past participle of flamber "to singe, blaze" (16c.), from Old French flambe "a flame" (see flamboyant). Middle English had flame (v.) in cookery sense "baste (a roast) with hot grease, to baste; to glaze (pastry)."
flambeau (n.) Look up flambeau at Dictionary.com
also flambeaux, 1630s, "flaming torch," from French flambeau (14c.), from flambe "flame" (see flamboyant). By 1883 as "a large, decorative candlestick."
flamboyance (n.) Look up flamboyance at Dictionary.com
1849, from flamboyant + -ance. Related: Flamboyancy (1846).
flamboyant (adj.) Look up flamboyant at Dictionary.com
1832, originally in reference to a 15c.-16c. architectural style with wavy, flame-like curves, from French flamboyant "flaming, wavy," present participle of flamboyer "to flame," from Old French flamboiier "to flame, flare, blaze, glow, shine" (12c.), from flambe "a flame, flame of love," from flamble, variant of flamme, from Latin flammula "little flame" (see flame (n.)). Extended sense of "showy, ornate" is from 1879. Related: Flamboyantly.
flame (v.) Look up flame at Dictionary.com
Middle English flaumen, also flaumben, flomben, flamben, flamen, flammen, c. 1300 (implied in flaming "to shine (like fire), gleam, sparkle like flames;" mid-14c. as "emit flames, be afire, to blaze," from Anglo-French flaumer, flaumber (Old French flamber) "burn, be on fire, be alight" (intransitive), from flamme "a flame" (see flame (n.)).

Transitive meaning "to burn, set on fire" is from 1580s. Meaning "break out in violence of passion" is from 1540s; the sense of "unleash invective on a computer network" is from 1980s. Related: Flamed; flaming. To flame out, in reference to jet engines, is from 1950.
flame (n.) Look up flame at Dictionary.com
Middle English flaume, also flaumbe, flambe, flame, flamme, mid-14c., "a flame;" late 14c., "a flaming mass, a fire; fire in general, fire as an element;" also figurative, in reference to the "heat" or "fire" of emotions, from Anglo-French flaume, flaumbe "a flame" (Old French flambe, 10c.), from Latin flammula "small flame," diminutive of flamma "flame, blazing fire," from PIE *bhleg- "to shine, flash," from root *bhel- (1) "to shine, flash, burn" (see bleach (v.)).

The meaning "a sweetheart, object of one's passion" is attested from 1640s; the figurative sense of "burning passion" was in Middle English, and the nouns in Old French and Latin also meant "fire of love, flame of passion," and, in Latin "beloved object." The Australian flame-tree is from 1857, so called for its red flowers.
flame-thrower (n.) Look up flame-thrower at Dictionary.com
also Flamethrower, 1917, translating German flammenwerfer (1915). See flame (n.) + throw (v.).
flamen (n.) Look up flamen at Dictionary.com
"ancient Roman priest," 1530s, from Latin flamen "a priest of one deity," which is of unknown origin, perhaps from PIE root *bhlad- "to worship" (cognates: Gothic blotan, Old English blotan "to sacrifice"). Also used from early 14c., in imitation of Geoffrey of Monmouth, in reference to ancient pre-Christian British priests. Related: Flamineous.
The old connection of flamen with Skt. brahman- is highly problematic, and has been dismissed by Schrijver. As WH surmise, the ending -en points to an archaism, probably a n[euter] noun "sacrificial act" which changed its semantics to 'priest'; for a similar shift, cf. augur "bird-observer" .... The only viable comparanda are found in [Germanic], but they show root-final (or suffixal) *-d~. [de Vaan]
flamenco (n.) Look up flamenco at Dictionary.com
1882, from Spanish flamenco, first used of Gypsy dancing in Andalusia. The word in Spanish meant "a Fleming, native of Flanders" (Dutch Vlaming) and also "flamingo." Speculation are varied and colorful about the connection between the bird, the people, and the gypsy dance of Andalusia.

Spain ruled Flanders for many years in 16c., and King Carlos I brought with him to Madrid an entire Flemish court. One etymology suggests the dance was so called from the bright costumes and energetic movements, which the Spanish associated with Flanders; another is that Spaniards, especially Andalusians, like to name things by their opposites, and because the Flemish were tall and blond and the gypsies short and dark, the gypsies were called "Flemish;" others hold that flamenco was the general Spanish word for all foreigners, gypsies included; or that Flemish noblemen, bored with court life, took to slumming among the gypsies. Compare Gypsy.
flamer (n.) Look up flamer at Dictionary.com
1590s, agent noun from flame (v.). Figurative sense "glaringly conspicuous person" is from 1809. For homosexual slang sense, see flaming.
flaming (adj.) Look up flaming at Dictionary.com
late 14c., "flame-like in appearance;" c. 1400, "on fire," present participle adjective from flame (v.). Meaning "of bright or gaudy colors" is from mid-15c. As an intensifying adjective, late 19c. Meaning "glaringly homosexual" is homosexual slang, 1970s (along with flamer (n.) "conspicuously homosexual man"); but flamer "glaringly conspicuous person or thing" (1809) and flaming "glaringly conspicuous" (1781) are much earlier in a general sense, both originally with reference to "wenches." Related: Flamingly.
flamingo (n.) Look up flamingo at Dictionary.com
long-legged, long-necked brightly colored pink bird of the tropical Americas, 1560s, from Portuguese flamengo, Spanish flamengo, literally "flame-colored" (compare Greek phoinikopteros "flamingo," literally "red-feathered"), from Provençal flamenc, from flama "flame" (see flame (n.)) + Germanic suffix -enc "-ing, belonging to." Perhaps accommodated to words for Fleming (see flamenco).
flammable (adj.) Look up flammable at Dictionary.com
1813, from stem of Latin flammare "to set on fire" (from flamma; see flame (n.)) + -able. In modern (20c.) use, a way to distinguish from the ambiguity of inflammable.
flan (n.) Look up flan at Dictionary.com
"open tart," 1846, from French flan "custard tart, cheesecake," from Old French flaon "flat-cake, tart, flan" (12c.), from Medieval Latin flado (10c.), which probably is from Frankish *flado or another Germanic source (compare Old High German flado "offering cake," Middle High German vlade "a broad, thin cake," Dutch vla "baked custard"), from Proto-Germanic *flatho(n) "flat cake," probably from PIE root *plat- "to spread" (see plaice (n.)). Borrowed earlier as flawn (c. 1300), from Old French.
Flanders Look up Flanders at Dictionary.com
from a source akin to Dutch Vlaanderen probably a compound of roots represented by Flemish vlakte "plain" + wanderen "to wander."
flaneur (n.) Look up flaneur at Dictionary.com
"habitual loafer, idle man about town," 1854, from French flâneur, from flâner "to stroll, loaf, saunter," probably from a Scandinavian source (compare Old Norse flana "to wander aimlessly," Norwegian flana, flanta "to gad about"), perhaps from PIE *pele- (2) "flat, to spread." Related: flânerie.
flange (n.) Look up flange at Dictionary.com
1680s, "a widening or branching out," of unknown origin, perhaps related to Old French flanche "flank, hip, side," fem. of flanc (see flank (n.)). Meaning "projecting rim, etc., used for strength or guidance" is from 1735. As a verb from 1820.
flank (n.) Look up flank at Dictionary.com
late Old English flanc "flank, fleshy part of the side," from Old French flanc "hip, side," from Frankish or another Germanic source, from Proto-Germanic *hlanca- (cognates: Old High German (h)lanca, Middle High German lanke "hip joint," German lenken "to bend, turn aside;" Old English hlanc "loose and empty, slender, flaccid;" Old Norse hlykkr "a bend, noose, loop"), from PIE root *kleng- "to bend, turn" (see link (n.)). Showing characteristic change of Germanic hl- to Romanic fl-. The military sense is first attested 1540s. Meaning "side" of anything is by 1620s. As an adjective, "pertaining to the flank or side," 1660s. Related: Flanked; flanking.
flank (v.) Look up flank at Dictionary.com
1590s (military), "to guard the flank," also, "to menace the flank, fire sideways upon," from flank (n.). Meaning "stand or be placed at the side of" is from 1650s. Related: Flanked; flanking.
flanker (n.) Look up flanker at Dictionary.com
1550s, from flank (n.).
flannel (n.) Look up flannel at Dictionary.com
"warm, loosely woven woolen stuff," c. 1300, flaunneol, probably related to Middle English flanen "sackcloth" (c. 1400); by Skeat and others traced to Welsh gwlanen "woolen cloth," from gwlan "wool," from Celtic *wlana, from PIE *wele- (1) "wool" (see wool). "As flannel was already in the 16th c. a well-known production of Wales, a Welsh origin for the word seems antecedently likely" [OED].

The Welsh origin is not a universally accepted etymology, due to the sound changes involved; Barnhart, Gamillscheg, Diez suggest the English word is from an Anglo-French diminutive of Old French flaine "a kind of coarse wool." Modern French flanelle is a 17c. borrowing from English.
flap (n.) Look up flap at Dictionary.com
mid-14c., flappe "a blow, slap, buffet," probably imitative of the sound of striking. Sense of "device for slapping or striking" is from early 15c. Meaning "something that hangs down" is first recorded 1520s, probably from flap (v.). Sense of "motion or noise like a bird's wing" is 1774; meaning "disturbance, noisy tumult" is 1916, British slang.
flap (v.) Look up flap at Dictionary.com
early 14c., "dash about, shake, beat (the wings);" later "strike, hit" (mid-14c.); probably ultimately imitative. Meaning "to swing about loosely" is from 1520s. Related: Flapped; flapping.
flapdoodle (n.) Look up flapdoodle at Dictionary.com
1833, originally "the stuff they feed fools on" [Marryat]; probably an arbitrary formation from elements meant to sound ridiculous, perhaps with allusions to flap "a stroke, blow" and doodle "fool, simpleton."
flapjack (n.) Look up flapjack at Dictionary.com
pre-1600, from flap (v.) + jack (n.), using the personal name in its "generic object" sense. So called from the process of baking it by flipping and catching it in the griddle when done on one side.
flapper (n.) Look up flapper at Dictionary.com
1560s, "one who or that which flaps," agent noun from flap (v.). Sense of "forward young woman" is 1921 slang, but the exact connection is disputed. Perhaps from flapper "young wild-duck or partridge" (1747), with reference to flapping wings while learning to fly, many late 19c. examples of which are listed in Wright's "English Dialect Dictionary" (1900), including one that defines it as "A young partridge unable to fly. Applied in joke to a girl of the bread-and-butter age."

Other suggested sources include a late 19c. northern English dialectal use of the word for "teen-age girl" (on notion of one with the hair not yet put up), or an earlier meaning "prostitute" (1889), which is perhaps from dialectal flap "young woman of loose character" (1610s). Any or all of these might have converged in the 1920s sense. Wright also has flappy, of persons, "wild, unsteady, flighty," with the note that it also was "Applied to a person's character, as 'a flappy lass,'" and further on he lists flappy sket (n.) "an immoral woman." In Britain the word took on political tones in reference to the debate over voting rights.
"Flapper" is the popular press catch-word for an adult woman worker, aged twenty-one to thirty, when it is a question of giving her the vote under the same conditions as men of the same age. ["Punch," Nov. 30, 1927]
flare (v.) Look up flare at Dictionary.com
1540s, "spread out" (hair), of unknown origin, perhaps from Scandinavian or from Dutch vlederen. Meaning "shine out with a sudden light" is from 1630s. The notion of "spreading out in display" is behind the notion of "spreading gradually outward" (1640s). Related: Flared; flaring.
flare (n.) Look up flare at Dictionary.com
"a giving off of a bright, unsteady light," 1814, from flare (v.). This led to the sense of "signal fire" (1883). The astronomy sense is from 1937. Meaning "a gradual widening or spreading" is from 1910; hence flares "flared trousers" (1964).