flatboat (n.) Look up flatboat at Dictionary.com
1650s, from flat (adj.) + boat (n.).
flatfish (n.) Look up flatfish at Dictionary.com
1710, from flat (adj.) + fish (n.).
flatline (v.) Look up flatline at Dictionary.com
by 1998, from the flat line on an electrocardiogram or electroencephalogram when the patient is dead. Related: Flatlined; flatlining.
flatly (adv.) Look up flatly at Dictionary.com
early 15c., in a literal sense, from flat (adj.) + -ly (2). Meaning "in a plain manner" is from 1560s; sense of "in a dull manner" is from 1640s.
flatness (n.) Look up flatness at Dictionary.com
mid-15c., from flat (adj.) + -ness.
flats (n.) Look up flats at Dictionary.com
"level tidal tract," 1540s, from flat (n.) "level piece of ground" (late 12c.), from flat (adj.).
flatten (v.) Look up flatten at Dictionary.com
late 14c., "to prostrate oneself," also "to fall flat," from flat (adj.) + -en (1). Meaning "to make flat" is 1620s. Related: Flattened; flattening.
flatter (v.) Look up flatter at Dictionary.com
early 13c., from Old French flater "to flatter" (13c.), originally "stroke with the hand, caress," from Frankish *flat "palm, flat of the hand" (see flat (adj.)). "[O]ne of many imitative verbs beginning with fl- and denoting unsteady or light, repeated movement" [Liberman]. Related: Flattered; flattering.
flatterer (n.) Look up flatterer at Dictionary.com
mid-14c., agent noun from flatter. Fem. form flatteress is attested from late 14c.-18c.
flattering (adj.) Look up flattering at Dictionary.com
late 14c., "pleasing to the imagination," present participle adjective from flatter. Meaning "gratifying to self-esteem" is from 1757. Related: Flatteringly.
flattery (n.) Look up flattery at Dictionary.com
early 14c., from Old French flaterie, from flater (see flatter).
flatulence (n.) Look up flatulence at Dictionary.com
1711, from French flatulence, from flatulent (see flatulent). Flatulency is from 1650s.
flatulent (adj.) Look up flatulent at Dictionary.com
1590s, from Middle French flatulent, from Modern Latin flatulentus, from Latin flatus "a blowing, a breaking wind," past participle of flare "to blow, puff," which is cognate with Old English blawan (see blow (v.1)).
flatus (n.) Look up flatus at Dictionary.com
1660s, from Latin flatus "a blowing," from flare "to blow" (see blow (v.1)).
flatware (n.) Look up flatware at Dictionary.com
1851, from flat (adj.) + ware (n.). Originally as distinguished from hollow ware; U.S. sense of "domestic cutlery" recorded by 1895.
flaunt (v.) Look up flaunt at Dictionary.com
1560s, "to display oneself in flashy clothes," of unknown origin; perhaps a variant of flout or vaunt. It looks French, but it corresponds to no known French word. Transitive sense is from 1827. Related: Flaunted; flaunting.
flautist (n.) Look up flautist at Dictionary.com
1860, from Italian flautista, from flauto "flute" (from Late Latin flauta; see flute (n.)) + Greek-derived suffix -ista.
Flavius Look up Flavius at Dictionary.com
masc. proper name, from Latin Flavius, a Roman gens name, related to flavus "golden-yellow, blond" (see blue), and probably originally meaning "yellow-haired."
flavor (n.) Look up flavor at Dictionary.com
c.1300, "a smell, odor" (usually a pleasing one), from Old French flaour "smell, odor," from Vulgar Latin flator "odor," literally "that which blows," from Latin flator "blower," from flare "to blow, puff," which is cognate with Old English blawan (see blow (v.1)).

The same Vulgar Latin source produced Old Italian fiatore "a bad odor." Sense of "taste, savor" is 1690s, perhaps 1670s; originally "the element in taste which depends on the sense of smell." The -v- is perhaps from influence of savor.
flavor (v.) Look up flavor at Dictionary.com
1730s, from flavor (n.). Related: Flavored; flavoring.
flavorful (adj.) Look up flavorful at Dictionary.com
1927, from flavor (n.) + -ful. Earlier flavorsome (1853), flavory (1727), flavorous (1690s).
flavoring (n.) Look up flavoring at Dictionary.com
1845, "thing that gives flavor," verbal noun from flavor (v.). Middle English flauryng meant "perfume."
flavour Look up flavour at Dictionary.com
chiefly British English spelling of flavor; for spelling, see -or. Related: Flavourful; flavouring.
flaw (n.) Look up flaw at Dictionary.com
early 14c., "a flake" (of snow), also in Middle English "a spark of fire; a splinter," from Old Norse flaga "stone slab, flake" (see flagstone); sense of "defect, fault" first recorded 1580s, first of character, later (c.1600) of material things; probably via notion of a "fragment" broken off.
flaw (v.) Look up flaw at Dictionary.com
early 15c. (implied in flawed); see flaw (n.). Related: Flawing.
flawless (n.) Look up flawless at Dictionary.com
1640s, from flaw + -less. Related: Flawlessly; flawlessness.
flax (n.) Look up flax at Dictionary.com
Old English fleax "cloth made with flax, linen," from Proto-Germanic *flakhsan (cognates: Old Frisian flax, Middle Dutch and Dutch vlas, Old Saxon flas, Old High German flahs, German Flachs), probably from Proto-Germanic base *fleh-, corresponding to PIE *plek- "to weave, plait" (see ply (v.1)). But some connect it with PIE *pleik- (see flay) from the notion of "stripping" fiber to prepare it.
flaxen (adj.) Look up flaxen at Dictionary.com
"made of flax," mid-15c., from flax + -en (2). As "the color of flax" (usually with reference to hair) it is attested from 1520s.
flaxseed (n.) Look up flaxseed at Dictionary.com
1560s, from flax + seed (n.).
flay (v.) Look up flay at Dictionary.com
Old English flean "to skin" (strong verb, past tense flog, past participle flagen), from Proto-Germanic *flahan (cognates: Middle Dutch vlaen, Old High German flahan, Old Norse fla), from PIE root *pl(e)ik-, *pleik- "to tear" (cognates: Lithuanian plešiu "to tear"). Related: Flayed; flaying.
flea (n.) Look up flea at Dictionary.com
Old English flea, from Proto-Germanic *flauhaz (cognates: Old Norse flo, Middle Dutch vlo, German Floh), perhaps related to Old English fleon "to flee," with a notion of "the jumping parasite," or perhaps from PIE *plou- "flea" (cognates: Latin pulex, Greek psylla; see puce).

Flea-bag "bed" is from 1839; flea circus is from 1886; flea collar is from 1953.
"A man named 'Mueller' put on the first trained-flea circus in America at the old Stone and Austin museum in Boston nearly forty years ago. Another German named 'Auvershleg' had the first traveling flea circus in this country thirty years ago. In addition to fairs and museums, I get as high as $25 for a private exhibition." ["Professor" William Heckler, quoted in "Popular Mechanics," February 1928. Printed at the top of his programs were "Every action is visible to the naked eye" and "No danger of desertion."]
flea market (n.) Look up flea market at Dictionary.com
1917, especially in reference to the marché aux puces in Paris, so-called "because there are so many second-hand articles sold of all kinds that they are believed to gather fleas." [E.S. Dougherty, "In Europe," 1922].
fleam (n.) Look up fleam at Dictionary.com
"sharp instrument for opening veins in bloodletting," late Old English, from Old French flieme (Modern French flamme), from Medieval Latin fletoma, from Late Latin flebotomus, from Greek phlebotomos "a lancet" (see phlebotomy).
fleck (v.) Look up fleck at Dictionary.com
late 14c., probably from Old Norse flekka "to spot," from Proto-Germanic *flekk- (cognates: Middle Dutch vlecke, Old High German flec, German Fleck), from PIE *pleik- "to tear" (see flay). Related: Flecked; flecking.
fleck (n.) Look up fleck at Dictionary.com
1590s, from fleck (v.) or else from Middle Dutch vlecke or Old Norse flekkr.
fled Look up fled at Dictionary.com
past tense and past participle of flee (q.v.).
fledge (v.) Look up fledge at Dictionary.com
Old English *-flycge (Kentish -flecge),an adjective meaning "having the feathers, fit to fly," from West Germanic *fluggja- (cognates: Middle Dutch vlugge, Low German flügge), from root meaning "to fly" (see fly (v.)). As a verb, it is first attested in English 1560s. Related: Fledged; fledging.
fledgling Look up fledgling at Dictionary.com
1830 (adj.), 1846 as a noun meaning "young bird," from fledge + diminutive suffix -ling. Of persons, from 1856.
flee (v.) Look up flee at Dictionary.com
Old English fleon "take flight, fly from, avoid, escape" (contracted class II strong verb; past tense fleah, past participle flogen), from Proto-Germanic *fleuhan (cognates: Old High German fliohan, Old Norse flöja, Old Frisian flia, Dutch vlieden, German fliehen, Gothic þliuhan "to flee"), possibly from PIE *pleu- "to flow" (see pluvial).

Weak past tense and past participle fled emerged Middle English, under influence of Scandinavian. Old English had a transitive form, geflieman "put to flight," which came in handy in the Anglo-Saxon Chronicle. Related: Fleeing.
fleece (v.) Look up fleece at Dictionary.com
1530s in the literal sense of "to strip a sheep of fleece;" 1570s in the figurative meaning "to cheat, swindle," from fleece (n.). Related: Fleeced; fleecing.
fleece (n.) Look up fleece at Dictionary.com
Old English fleos, from West Germanic *flusaz (cognates: Middle Dutch vluus, Dutch vlies, Middle High German vlius, German Vlies), probably from PIE *pleus- "to pluck," also "a feather, fleece" (cognates: Latin pluma "feather, down," Lithuanian plunksna "feather").
fleecy (adj.) Look up fleecy at Dictionary.com
1560s, from fleece (n.) + -y (2).
fleer (v.) Look up fleer at Dictionary.com
c.1400, perhaps from Scandinavian (compare dialectal Norwegian flira, dialectal Danish flire "to grin, titter"). Related: Fleered; fleering.
fleet (n.) Look up fleet at Dictionary.com
Old English fleot "ship, raft, floating vessel," from fleotan "to float" (see fleet (v.)). Sense of "naval force" is pre-1200. The Old English word also meant "creek, inlet, flow of water," especially one into the Thames near Ludgate Hill, which lent its name to Fleet Street (home of newspaper and magazine houses, standing for "the English press" since 1882), Fleet prison, etc.
fleet (adj.) Look up fleet at Dictionary.com
"swift," 1520s, but probably older than the record; apparently from or cognate with Old Norse fliotr "swift," and from the root of fleet (v.)). Related: Fleetness.
fleet (v.) Look up fleet at Dictionary.com
Old English fleotan "to float, drift, flow, swim, sail," later (c.1200) "to flow," from Proto-Germanic *fleut- (cognates: Old Frisian fliata, Old Saxon fliotan "to flow," Old High German fliozzan "to float, flow," German flieszen "to flow," Old Norse fliota "to float, flow"), from PIE root *pleu- "to flow, run, swim" (see pluvial).

Meaning "to glide away like a stream, vanish imperceptibly" is from c.1200; hence "to fade, to vanish" (1570s). Related: Fleeted; fleeting.
fleeting (adj.) Look up fleeting at Dictionary.com
early 13c., "fickle, shifting, unstable," from Old English fleotende "floating, drifting," later "flying, moving swiftly," from present participle of fleotan (see fleet (v.)). Meaning "existing only briefly" is from 1560s.
Fleming (n.) Look up Fleming at Dictionary.com
Old English Flæming "native or inhabitant of Flanders," and Old Frisian Fleming, from Proto-Germanic *Flam- (source also of Medieval Latin Flamingus); see Flanders.
Flemish (adj.) Look up Flemish at Dictionary.com
early 14c., flemmysshe, probably from Old Frisian Flemische, or from Fleming + -ish.
flense (v.) Look up flense at Dictionary.com
also flench, 1814, from Danish flense, perhaps from PIE root *(s)plei- "to splice, split." Related: Flenser; flensing.