fortitudinous (adj.) Look up fortitudinous at Dictionary.com
from Latin fortitudinem (nominative fortitudo; see fortitude) + -ous. Related: Fortitudinously.
fortnight (n.) Look up fortnight at Dictionary.com
17c. contraction of Middle English fourteniht, from Old English feowertyne niht, literally "fourteen nights," preserving the ancient Germanic custom of reckoning by nights, mentioned by Tacitus in "Germania" xi. Related: Fortnightly.
Fortran (n.) Look up Fortran at Dictionary.com
computer programming language, 1956, from combination of elements from formula + translation.
fortress (n.) Look up fortress at Dictionary.com
early 14c., from Old French forteresse "strong place" (12c.), variant of fortelesse, from Medieval Latin fortalitia, from Latin fortis "strong" (see fort) + English -ess, a fairly uncommon suffix (duress, largess being other examples), from Latin -itia, forming nouns of quality or condition.
fortuitous (adj.) Look up fortuitous at Dictionary.com
1650s, from Latin fortuitus "happening by chance, casual, accidental," from forte "by chance," ablative of fors "chance" (related to fortuna; see fortune). It means "accidental, undesigned" not "fortunate." Earlier in this sense was fortuit (late 14c.), from French. Related: Fortuitously; fortuitousness.
fortuity (n.) Look up fortuity at Dictionary.com
1747, from fortuitous + -ity.
fortunate (adj.) Look up fortunate at Dictionary.com
late 14c., from Latin fortunatus "prospered, prosperous; lucky, happy," past participle of fortunare "to make prosperous," from fortuna (see fortune). Fortunate Islands "mythical abode of the blessed dead, in the Western Ocean," early 15c., translates Latin Fortunatae Insulae.
fortunately (adv.) Look up fortunately at Dictionary.com
1540s, from fortunate + -ly (2).
fortune (n.) Look up fortune at Dictionary.com
c.1300, "chance, luck as a force in human affairs," from Old French fortune "lot, good fortune, misfortune" (12c.), from Latin fortuna "chance, fate, good luck," from fors (genitive fortis) "chance, luck," possibly from PIE *bhrtu- and related to base *bher- (1) "to carry" (see infer).

Often personified as a goddess; her wheel betokens vicissitude. Sense of "owned wealth" first found in Spenser; probably it evolved from senses of "one's condition or standing in life," hence "position as determined by wealth," then "wealth" itself. Soldier of fortune first attested 1660s. Fortune 500 "most profitable American companies" is 1955, from the list published annually in "Fortune" magazine.
fortune cookie (n.) Look up fortune cookie at Dictionary.com
by 1955, said to have been invented in 1918 by David Jung, Chinese immigrant to America who established Hong Kong Noodle Co., who handed out cookies that contained uplifting messages as a promotional gimmick.
fortuneteller (n.) Look up fortuneteller at Dictionary.com
also fortune-teller, 1580s, from fortune + teller. Verbal phrase tellen fortune is from early 15c.
forty (n.) Look up forty at Dictionary.com
Old English feowertig, from feower "four" (see four) + tig "group of ten" (see -ty (1)). Compare Old Saxon fiwartig, Old Frisian fiuwertich, Dutch veertig, Old High German fiorzug, German vierzig, Old Norse fjorir tigir, Gothic fidwor tigjus.
[T]he number 40 must have been used very frequently by Mesha's scribe as a round number. It is probably often used in that way in the Bible where it is remarkably frequent, esp. in reference to periods of days or years. ... How it came to be so used is not quite certain, but it may have originated, partly at any rate, in the idea that 40 years constituted a generation or the period at the end of which a man attains maturity, an idea common, it would seem, to the Greeks, the Israelites, and the Arabs. ["The International Standard Bible Encyclopedia," James Orr, ed., Chicago, 1915]
Forty winks "short sleep" is attested from 1821, In early use associated with, and perhaps coined by, eccentric English lifestyle reformer William Kitchiner M.D. (1775-1827).
forum (n.) Look up forum at Dictionary.com
mid-15c., "place of assembly in ancient Rome," from Latin forum "marketplace, open space, public place," apparently akin to foris, foras "out of doors, outside," from PIE root *dhwer- (see door). Sense of "assembly, place for public discussion" first recorded 1680s.
forward (adv.) Look up forward at Dictionary.com
Old English forewearde "toward the front;" see fore + -ward. Adjectival sense of "early" is from 1520s; that of "presumptuous" is attested from 1560s.
forward (v.) Look up forward at Dictionary.com
1590s, "to help push forward," from forward (adv.). Meaning "to send (a letter, etc.) on to another destination" is from 1757. Related: Forwarded; forwarding.
forward (n.) Look up forward at Dictionary.com
Old English, "the fore or front part" of something; see forward (adv.). The position in football so called since 1879.
forwardness (n.) Look up forwardness at Dictionary.com
1520s, from forward (adj.) + -ness. Meaning "presumptuousness" is from c.1600.
forwards (adv.) Look up forwards at Dictionary.com
Middle English, from forward + adverbial genitive -s. British English until mid-20c. preserved the distinction between forward and forwards, the latter expressing "a definite direction viewed in contrast with other directions." In American English, however, forward prevails in all senses since Webster (1832) damned forwards as "a corruption."
Fosbury flop Look up Fosbury flop at Dictionary.com
high-jumping technique, 1968, in reference to U.S. athlete Dick Fosbury (b.1947), who used it to win the 1968 Olympic gold medal.
fosse (n.) Look up fosse at Dictionary.com
early 14c. (late 13c. in place names), "ditch, trench," mid-15c., from Old French fosse "ditch, grave, dungeon" (12c.), from Latin fossa "ditch," in full fossa terra, literally "dug earth," from fem. past participle of fodere "to dig" (see fossil).

The Fosse-way (early 12c.), one of the four great Roman roads of Britain, probably was so called from the ditch on either side of it.
fossil (n.) Look up fossil at Dictionary.com
1610s, "any thing dug up;" 1650s (adj.) "obtained by digging," from French fossile (16c.), from Latin fossilis "dug up," from fossus, past participle of fodere "to dig," from PIE root *bhedh- "to dig, pierce."

Restricted noun sense of "geological remains of a plant or animal" is from 1736; slang meaning "old person" first recorded 1859. Fossil fuel (1835) preserves the earlier, broader sense.
fossiliferous (adj.) Look up fossiliferous at Dictionary.com
by 1830, from fossil + -ferous "producing, containing," from ferre "to bear" (see infer).
fossilize (v.) Look up fossilize at Dictionary.com
1794, from fossil + -ize. Figurative use from 1856. Related: Fossilized; fossilizing.
foster (v.) Look up foster at Dictionary.com
Old English *fostrian "to supply with food, nourish, support," from fostor "food, nourishment, bringing up," from Proto-Germanic *fostrom, from root *foth-/*fod- (see food).

Meaning "to bring up a child with parental care" is from c.1200; that of "to encourage or help grow" is early 13c. of things; 1560s of feelings, ideas, etc. Old English also had the adjective meaning "in the same family but not related," in fostorfæder, etc. Related: Fostered; fostering.
fought Look up fought at Dictionary.com
past tense and past participle of fight (v.). The past participle form foughten (Old English fohten) has been archaic since 18c. but occasionally appears in the phrase foughten field.
foul (adj.) Look up foul at Dictionary.com
Old English ful "rotten, unclean, vile, corrupt, offensive to the senses," from Proto-Germanic *fulaz (cognates: Old Saxon and Old Frisian ful, Middle Dutch voul, Dutch vuil, Old High German fül, German faul, Gothic füls), from root *fu-, corresponding to PIE *pu-, perhaps from the sound made in reaction to smelling something bad (compare Sanskrit puyati "rots, stinks," putih "foul, rotten;" Greek puon "discharge from a sore;" Latin pus "putrid matter," putere "to stink," putridus "rotten;" Lithuanian puviu "to rot").

Old English ful occasionally meant "ugly" (as contrasted with fæger (adj.), modern fair (adj.)), a sense frequently found in Middle English, and the cognate in Swedish is the usual word for "ugly." Of weather, first recorded late 14c. In the sporting sense of "irregular, unfair" it is first attested 1797, though foul play is recorded from mid-15c. Baseball sense of "out of play" attested by 1860. Foulmart was a Middle English word for "polecat" (from Old English mearð "marten").
foul (v.) Look up foul at Dictionary.com
Old English fulian "to become foul, rot," from ful (see foul (adj.)). Related: Fouled; fouling.
foul-mouthed (adj.) Look up foul-mouthed at Dictionary.com
also foulmouthed, 1590s, apparently first in Shakespeare ["Henry IV," 1596].
foully (adv.) Look up foully at Dictionary.com
Old English fullice; see foul (adj.) + -ly (2).
foulness (n.) Look up foulness at Dictionary.com
Old English fulness "foulness, filthy smell;" see foul (adj.) + -ness.
found (v.1) Look up found at Dictionary.com
"establish," late 13c., from Old French founder (12c., Modern French fonder), from Latin fundare "to lay the bottom or foundation of something," from fundus "bottom, foundation" (see fund (n.)). Related: Founded; founding. Phrase founding fathers with reference to the creators of the American republic is attested from 1916.
found (v.2) Look up found at Dictionary.com
"cast metal," late 14c., "to mix, mingle," from Middle French fondre "pour out, melt, mix together," from Old French fondre, from Latin fundere "melt, cast, pour out," from PIE *gheud- (cognates: Gothic giutan, German gießen, Old English geotan "to pour"), from root *gheu- "to pour" (cognates: Greek khein "to pour," khoane "funnel," khymos "juice"). Meaning "to cast metal" is from 1560s.
found (adj.) Look up found at Dictionary.com
"discovered," late 14c., past participle adjective from find (v.). Expression and found in old advertisements for job openings, travelling berths, etc., attached to the wages or charges, indicates that meals are provided, from the expression to find one's self "to provide for one's self." "When a laborer engages to provide himself with victuals, he is said to find himself, or to receive day wages" [Bartlett, "Dictionary of Americanisms," 1848]. Hence, so much and found for "wages + meals provided."
foundation (n.) Look up foundation at Dictionary.com
late 14c., "action of founding," from Old French fondacion (14c.) or directly from Latin fundationem (nominative fundatio) "a founding," noun of action from past participle stem of fundare (see found (v.1)). The Latin word is glossed in Old English by staþol. Meaning "that which is founded" (a college, hospital, etc.) is from 1510s; meaning "funds endowed" is early 15c. Sense of "solid base of a structure" is from late 15c.
foundational (adj.) Look up foundational at Dictionary.com
1680s, from foundation + -al (1).
founder (v.) Look up founder at Dictionary.com
early 14c., from Old French fondrer "collapse; submerge, sink, fall to the bottom," from fond "bottom," from Latin fundus "bottom, foundation" (see fund (n.)). Related: Foundered; foundering.
founder (n.1) Look up founder at Dictionary.com
"one who establishes, one who sets up or institutes something," mid-14c., from Anglo-French fundur, Old French fondeor, from Latin fundator, agent noun from fundare (see found (v.1)).
founder (n.2) Look up founder at Dictionary.com
"one who casts metal," c.1400, agent noun from found (v.2).
foundling (n.) Look up foundling at Dictionary.com
"deserted infant," c.1300, from Middle English founden "found," past participle of finden (see find (v.)) + diminutive suffix -ling. Compare Dutch vondeling, German Findling.
foundry (n.) Look up foundry at Dictionary.com
c.1600, from French fonderei, from fondre "to cast" (see found (v.2)).
fount (n.) Look up fount at Dictionary.com
mid-15c., probably a shortening of fountain, influenced by Middle French font "fount."
fountain (n.) Look up fountain at Dictionary.com
early 15c., "spring of water that collects in a pool," from Old French fontaine "natural spring" (12c.), from Late Latin fontana "fountain, spring" (source of Spanish and Italian fontana), from noun use of fem. of Latin fontanus "of a spring," from fons (genitive fontis) "spring (of water);" cognate with Sanskrit dhanvati "flows, runs."

The extended sense of "artificial jet of water" (and the structures that make them) is first recorded c.1500. "A French fountain-pen is described in 1658 and Miss Burney used one in 1789" [Weekley].
fountainhead (n.) Look up fountainhead at Dictionary.com
"spring from which a stream flows," 1580s, from fountain + head (n.). Figurative use is from c.1600.
four (n.) Look up four at Dictionary.com
Old English feower, from Proto-Germanic *fedwor- (cognates: Old Saxon fiwar, Old Frisian fiuwer, Frankish *fitter-, Dutch and German vier, Old Norse fjorir, Danish fire, Swedish fyra, Gothic fidwor "four"), from PIE *kwetwer- "four" (cognates: Sanskrit catvarah, Avestan čathwaro, Persian čatvar, Greek tessares, Latin quattuor, Oscan petora, Old Church Slavonic četyre, Lithuanian keturi, Old Irish cethir, Welsh pedwar). The phonetic evolution of the Germanic forms has not been fully explained; Watkins explains the -f- as being from the following number (Modern English five).

Slang four-eyes "person who wears glasses" first recorded 1874. Four-letter word first attested 1934; four-letter man, however, is recorded from 1923 (as a euphemism for a shit). A four-in-hand (1793) was a carriage with four horses driven by one person; in the sense of "loosely tied necktie" it is attested from 1892. To study The History of the Four Kings (1760, compare French Livres des Quatre Rois) contains euphemistic slang phrase for "a pack of cards" from the time when card-playing was considered a wicked pastime for students. Slang 4-1-1 "essential information" (by 1993) is from the telephone number called to get customer information.
four-door (adj.) Look up four-door at Dictionary.com
of cars, 1957, from four + door.
four-flusher (n.) Look up four-flusher at Dictionary.com
"cheat, dishonest person," 1900, from verb four-flush "to bluff a poker hand, claim a flush (n.) while holding only four cards in the suit" (1896).
four-footed (adj.) Look up four-footed at Dictionary.com
Old English feowerfote; see four + foot (n.).
fourfold (adj.) Look up fourfold at Dictionary.com
Old English feowerfeald; see four + -fold.
Fourierism (n.) Look up Fourierism at Dictionary.com
1841, in reference to ideas of French socialist François-Marie-Charles Fourier (1772-1837), whose plan also was called phalansterianism.
fourscore (n.) Look up fourscore at Dictionary.com
"eighty," mid-13c., "formerly current as an ordinary numeral" [OED], from four + score (n.).