Online Etymology Dictionary

fettuccini: see fettuccine.
fetus (n.): late 14c., "the young while in the womb or egg," from Latin fetus (often, incorrectly, foetus) "the bearing, bringing forth, or hatching of young," from Latin base *fe- "to generate, bear," also "to suck, suckle" (see fecund).

In Latin, fetus sometimes was transferred figuratively to the newborn creature itself, or used in a sense of "offspring, brood" (cf. Horace's "Germania quos horrida parturit Fetus"), but this was not the basic meaning. Also used of plants, in the sense of "fruit, produce, shoot." The spelling foetus is sometimes attempted as a learned Latinism, but it is not historic.
feu de joie (n.): public bonfire, French, literally "fire of joy."
feud (n.): c.1300, fede "enmity, hatred, hostility," northern English and Scottish; perhaps from an unrecorded Old English word or else from Old French fede, from Old High German fehida "contention, quarrel, feud," from Proto-Germanic *faihitha noun of state from adj. *faiho- (cf. Old English fæhð "enmity," fah "hostile;" German Fehde "feud;" Old Frisian feithe "enmity;" see foe). Sense of "vendetta" is early 15c. Alteration of spelling in 16c. is unexplained.
feud (v.): 1670s, from feud (n.). Related: Feuded; feuding.
feudal (adj.): 1610s, from Medieval Latin feudalis, from feudum "feudal estate," of Germanic origin (cf. Gothic faihu "property," Old High German fihu "cattle;" see fee). Related to Middle English feodary "one who holds lands of an overlord in exchange for service" (late 14c.).
feudalism (n.): a coinage of historians, first attested 1839; see feudal. Feudal system attested from 1776.
feuilleton (n.): part of a French newspaper devoted to light literature and criticism (usually at the bottom of a page and separated by a rule), 1845, from French feuilleton (18c.), literally "a leaflet (added to a newspaper)," diminutive of feuille "leaf," from Latin folium (see folio).
Esp. applied in F. to the short story or serial with which newspapers filled up after the fall of Napoleon left them short of war news. This was the beginning of Dumas' and Eugène Sue's long novels. [Weekley]
fever (n.): late Old English fefor, fefer "fever," from Latin febris "fever," related to fovere "to warm, heat," probably from PIE root *dhegh- "burn" (cf. Gothic dags, Old English dæg "day," originally "the heat"); but some suggest a reduplication of a root represented by Sanskrit *bhur- "to be restless."

Adopted into most Germanic languages (cf. German Fieber, Swedish feber, Danish feber), but not in Dutch. English spelling influenced by Old French fievre. Replaced Old English hriðing. Extended sense of "intense nervous excitement" is from 1580s.
feverfew (n.): Old English feferfuge, from Late Latin febrifugia, from Latin febris "fever" (see fever) + fugare "put to flight;" so called for its medical usage. The modern English word probably is from an Anglo-French source.
feverish (adj.): late 14c., "causing fever;" 1630s, "excited;" 1640s, "having symptoms of fever," from fever + -ish. Earlier in same sense was feverous (late 14c.). Related: Feverishly; feverishness.
feverously (adv.): late 14c., from fever + -ous. Related: Feverously.
few (adj.): Old English feawe (plural; contracted to fea) "few, seldom, even a little," from Proto-Germanic *faw-, from PIE root *pau- (1) "few, little" (cf. Latin paucus "few, little," paullus "little," parvus "little, small," pauper "poor;" Greek pauros "few, little," pais (genitive paidos) "child;" Latin puer "child, boy," pullus "young animal;" Oscan puklu "child;" Sanskrit potah "a young animal," putrah "son;" Old English fola "young horse;" Old Norse fylja "young female horse;" Old Church Slavonic puta "bird;" Lithuanian putytis "young animal, young bird"). Always plural in Old English.

Phrase few and far between attested from 1660s. Unusual ironic use in quite a few "many" (1883), earlier a good few (1828). The noun is late 12c., fewe, from the adjective.
Never in the field of human conflict was so much owed by so many to so few. [Winston Churchill, 1940]
fey (adj.): "of excitement that presages death," from Old English fæge "doomed to die, fated, destines," also "timid, feeble;" and/or from Old Norse feigr, both from Proto-Germanic *faigjo- (cf. Old Saxon fegi, Old Frisian fai, Middle Dutch vege, Middle High German veige "doomed," also "timid," German feige "cowardly"), from PIE *peig- "evil-minded, hostile" (see foe). Preserved in Scottish. Sense of "displaying unearthly qualities" and "disordered in the mind (like one about to die)" led to modern ironic sense of "affected."
fez (n.): 1802, from French fez, from Turkish fes, probably ultimately from Fez, the city in Morocco, where this type of tasseled cap was principally made.
fiance (n.): "man to whom one is betrothed," 1864, from French fiancé, past participle of fiancer "to betroth" (see fiancee).
fiancee (n.): "woman to whom one is betrothed," 1853, from French fianceé, fem. of fiancé, past participle of fiancer "to betroth," from fiance "a promise, trust," from fier "to trust," from Vulgar Latin *fidare (see affiance). Has all but expelled native betrothed. The verb fiance, now obsolete, was used c.1450-1600 for "to engage to be married."
fianchetto (n.): chess move, Italian, diminutive of fianco "flank" (attack), from Old French flanc "hip, side" (see flank (n.)).
fiasco (n.): 1855, theater slang for "a failure," by 1862 acquired the general sense of any dismal flop, on or off the stage. Via French phrase fiare fiasco "turn out a failure" (19c.), from Italian far fiasco "suffer a complete breakdown in performance," literally "make a bottle," from fiasco "bottle," from Late Latin flasco, flasconem (see flask).

The reason for all this is utterly obscure today, but "the usual range of fanciful theories has been advanced" [Ayto]. Weekley finds it utterly mysterious and compares French ramasser un pelle "to come a cropper (in bicycling), literally to pick up a shovel." OED makes nebulous reference to "alleged incidents in Italian theatrical history." Klein suggests Venetian glass-crafters tossing aside imperfect pieces to be made later into common flasks. But according to an Italian dictionary, fare il fiasco used to mean "to play a game so that the one that loses will pay the fiasco," in other words, he will buy the next bottle (of wine). That plausibly connects the word with the notion of "a costly mistake."
fiat (n.): "authoritative sanction," 1630s, from Latin fiat "let it be done" (also used in the opening of Medieval Latin proclamations and commands), third person singular present subjunctive of fieri, used as passive of facere "to make, do" (see factitious). Also sometimes a reference to fiat lux "let there be light" in the Book of Genesis.
fib (n.): 1610s, of uncertain origin, perhaps from fibble-fable "nonsense" (1580s), a reduplication of fable.
fib (v.): 1680s, from fib (n.). Related: Fibbed; fibbing.
fibber (n.): 1723, agent noun from fib (v.).
fiber (n.): 1530s, from French fibre (14c.), from Latin fibra "a fiber, filament," of uncertain origin, perhaps related to Latin filum "thread," or from root of findere "to split." Fiberboard is from 1897; Fiberglas is 1937, U.S. registered trademark name; and fiber optics is from 1956.
fibre (n.): chiefly British English spelling of fiber (q.v.); for spelling, see -re.
fibril (n.): 1680s, back-formation from Modern Latin fibrilla, diminutive of Latin fibra (see fiber).
fibrillate (v.): c.1840, from fibrilla (see fibril) + -ate (2). Related: Fibrillated; fibrillating.
fibrillation (n.): c.1840, noun of action from fibrillate.
fibrin (n.): blood-clotting substance, 1800, from Latin fibra (see fiber) + chemical suffix -in (2). So called because it is deposited as a network of fibers that cause the blood to clot.
fibromyalgia (n.): 1981, said to have been coined by U.S. rheumatologist Mohammed Yunus, from Latin fibra (see fiber) + Greek mys (genitive myos) "muscle" (see muscle) + -algia. The earlier name for the condition was fibrositis.
fibrosis (n.): 1873, a Modern Latin hybrid, from Latin fibra (see fiber) + Greek suffix -osis.
fibrous (adj.): 1620s, from Modern Latin fibrosus, from Latin fibra (see fiber).
fibula (n.): 1670s, "clasp, buckle, brooch;" 1706 as "smaller bone in the lower leg," from Latin fibula "clasp, brooch," related to figere "to fasten, fix" (see fix (v.)).

Used in reference to the outer leg bone as a loan-translation of Greek perone "small bone in the lower leg," originally "clasp, brooch; anything pointed for piercing or pinning;" the bone was so called because it resembles a clasp like a modern safety pin.
fiche (n.): 1949, "slip of paper, form," from French fiche "card, index card, slip, form," from Old French fichier "to attach, stick into, pin on," from Vulgar Latin *figicare, from Latin figere "to fix, fasten" (see fix (v.)). Sense of "card, strip of film" is a shortening of microfiche (1950).
fichu (n.): 1803, from French fichu (18c. in this sense), apparently a noun use of the adj. fichu "carelessly thrown on," from Latin figere "to fasten" (see fix). "[M]od. substitution for a coarser word" [Weekley].
fickle (adj.): c.1200, probably from Old English ficol "deceitful, cunning, tricky," related to befician "deceive," and to facen "deceit, treachery." Common Germanic (cf. Old Saxon fekan "deceit," Old High German feihhan "deceit, fraud, treachery"), from PIE *peig- "evil-minded, treacherous, hostile" (cf. Latin piget "it irks, troubles, displeases," piger "reluctant, lazy"). Sense of "changeable" is first recorded late 13c. Related: Fickleness.
fiction (n.): late 14c., "something invented," from Old French ficcion (13c.) "dissimulation, ruse; invention," and directly from Latin fictionem (nominative fictio) "a fashioning or feigning," noun of action from past participle stem of fingere "to shape, form, devise, feign," originally "to knead, form out of clay," from PIE *dheigh- (cf. Old English dag "dough;" see dough). As a branch of literature, 1590s.
fictional (adj.): "pertaining to fiction," 1843, from fiction + -al (1). Earlier fictitious also was used in this sense (1773).
fictionalization (n.): 1946, noun of action from fictionalize.
fictionalize (v.): 1925, from fictional + -ize. Related: Fictionalized; fictionalizing.
fictitious (adj.): 1610s, "artificial, counterfeit," from Medieval Latin fictitus, a misspelling of Latin ficticius "artificial, counterfeit," from fictus "feigned, fictitious, false," past participle of fingere (see fiction). Related: Fictitiously.
ficus (n.): c.1400, from Latin ficus "fig, fig tree" (see fig).
fiddle (n.): late 14c., fedele, earlier fithele, from Old English fiðele, which is related to Old Norse fiðla, Middle Dutch vedele, Dutch vedel, Old High German fidula, German Fiedel; all of uncertain origin.

Perhaps from Medieval Latin vitula "stringed instrument," which is perhaps related to Latin vitularia "celebrate joyfully," from Vitula, Roman goddess of joy and victory, who probably, like her name, originated among the Sabines [Klein, Barnhart]. Unless the Medieval Latin word is from the Germanic ones.

Fiddle has been relegated to colloquial usage by its more proper cousin, violin, a process encouraged by phraseology such as fiddlesticks, contemptuous nonsense word fiddlededee (1784), and fiddle-faddle. Fit as a fiddle is from 1610s.
fiddle (v.): late 14c., from fiddle (n.); the figurative sense of "to act nervously or idly" is from 1520s. Related: Fiddled; fiddling.
fiddle-faddle: 1570s (n.); 1630s (v.), apparently a reduplication of obsolete faddle "to trifle."
fiddlehead (n.): "one with a head as hollow as a fiddle," 1854 (fiddleheaded), from fiddle (n.) + head (n.). As a name for young fern fronds, from 1882, from resemblance to a violin's scroll.
fiddler (n.): late 13c., from Old English fiðelere "fiddler" (fem. fiðelestre), agent noun from fiddle (v.). Fiddler's Green first recorded 1825, from sailors' slang. Fiddler crab is from 1714.
fiddlestick (n.): usually fiddlesticks; 15c., originally "the bow of a fiddle," from fiddle (n.) and stick (n.). Meaning "nonsense" is from 1620s.
fideism (n.): 1885, from Latin fides "faith" (see faith) + -ism.
fidelity (n.): early 15c., from Middle French fidélité (15c.), from Latin fidelitatem (nominative fidelitas) "faithfulness, adherence," from fidelis "faithful, true," from fides "faith" (see faith).