flywheel (n.)
1784, from fly (n.) "speed-regulating device" (from fly (v.1)) + wheel (n.).
fo'c'sle (n.)
see forecastle.
foal (n.)
Old English fola "foal, colt," from Proto-Germanic *fulon (cognates: Old Saxon folo, Middle Dutch and Dutch veulen, Old Norse foli, Old Frisian fola, Old High German folo, German Fohlen, Gothic fula), from PIE *pulo- "young of an animal" (cognates: Greek polos "foal," Latin pullus "a young animal," Albanian pele "mare"), from root *pau- "few, little" (see few).
foal (v.)
"give birth (to a foal)," late 14c., from foal (n.). Related: Foaled; foaling.
foam (n.)
Old English fam "foam, saliva froth," from West Germanic *faimo- (cognates: Old High German veim, German Feim), from PIE *(s)poi-mo-, a root with connotations of "foam, froth" (cognates: Sanskrit phenah; Latin pumex "pumice," spuma "foam;" Old Church Slavonic pena "foam;" Lithuanian spaine "a streak of foam"). The rubber or plastic variety so called from 1937.
foam (v.)
Old English famgian "to foam," from the source of foam (n.). Related: Foamed; foaming.
foamy (adj.)
Old English faemig; see foam (n.) + -y (2). Related: Foaminess.
fob (n.)
1650s, "small pocket for valuables," probably related to Low German fobke "pocket," High German fuppe "pocket," "a dialectal word used in Livonia" [Klein]. Meaning "chain attached to a watch carried in the fob" is from 1885.
fob (v.)
"to cheat," late 14c., from obsolete noun fobbe "cheat, trickster" (late 14c.), perhaps from Old French forbe "cheat" [OED]. Alternative etymology holds that the word is perhaps related to German foppen "to jeer at, make a fool of" (see fop); or from German fuppen, einfuppen "to pocket stealthily," which would connect it to fob (n.). To fob (someone) off is first recorded 1590s. Related: Fobbed; fobbing.
focal (adj.)
1690s, from Modern Latin focalis; see focus (n.) + -al (1).
foci (n.)
plural of focus (n.).
focus (n.)
1640s, from Latin focus "hearth, fireplace" (also, figuratively, "home, family"), of unknown origin, used in post-classical times for "fire" itself, taken by Kepler (1604) in a mathematical sense for "point of convergence," perhaps on analogy of the burning point of a lens (the purely optical sense of the word may have existed before Kepler, but it is not recorded). Introduced into English 1650s by Hobbes. Sense transfer to "center of activity or energy" is first recorded 1796.
focus (v.)
1775 in the literal sense; 1807 in the figurative sense, from focus (n.). Related: Focused; focusing; less commonly focussed; focussing.
fodder (n.)
Old English fodder "food," especially "food for cattle," from Proto-Germanic *fodran (cognates: Old Norse foðr, Middle Dutch voeder, Old High German fuotar, German Futter), from PIE *patrom, from *pa- "to feed" (see food).
foe (n.)
Old English gefa "foe, enemy, adversary in a blood feud" (the prefix denotes "mutuality"), from fah "at feud, hostile," from Proto-Germanic *fakhaz (cognates: Old High German fehan "to hate," Gothic faih "deception"), probably from PIE root *peig- (2) "evil-minded, treacherous, hostile" (cognates: Sanskrit pisunah "malicious," picacah "demon;" Greek pikros "bitter;" Latin piget "it irks, troubles, displeases," piger "reluctant, lazy;" Lithuanian piktas "wicked, angry," pekti "to blame"). Weaker sense of "adversary" is first recorded c.1600.
foetal (adj.)
see fetal; for spelling, see oe.
foetid (adj.)
see fetid; for spelling, see oe.
foetus (n.)
see fetus; for spelling, see oe.
fog (v.)
1590s, from fog (n.1). Related: Fogged; fogging.
fog (n.1)
"thick, obscuring mist," 1540s, probably from a Scandinavian source akin to Danish fog "spray, shower, snowdrift," Old Norse fok "snow flurry," fjuk "snow storm." Compare also Old English fuht, Dutch vocht, German Feucht "moist." Figurative phrase in a fog "at a loss what to do" first recorded c.1600.
fog (n.2)
"long grass," c.1300, probably of Scandinavian origin; compare Norwegian fogg "long grass in a moist hollow," Icelandic fuki "rotten sea grass." The connection to fog (n.1), via a notion of long grass growing in moist dells of northern Europe, is tempting but not proven. Watkins suggests derivation from PIE *pu- "to rot, decay."
Fogarty
surname, from Old Irish fogartach "banished."
fogey (n.)
also fogy, "an old, dull fellow," 1780, Scottish foggie, originally "army pensioner or veteran," perhaps connected to fogram (1775) "old-fashioned person;" or from fog in obsolete senses of "moss" or "bloated fat" (1580s).
foggy (adj.)
1540s, perhaps from a Scandinavian source, or formed from fog (n.1) + -y (2). Foggy Bottom "U.S. Department of State," from the name of a marshy region of Washington, D.C., where many federal buildings are (also with a suggestion of political murkiness) popularized 1947 by James Reston in "New York Times," but he said it had been used earlier by Edward Folliard of "The Washington Post."
foghorn (n.)
1858, from fog (n.1) + horn (n.).
foible (n.)
1640s, "weak point of a sword blade" (contrasted to forte), from French foible (n.), from obsolete foible (adj.) "weak," from Old French foible "feeble," dissimilated from Lain flebilis (see feeble). Extended sense of "weak point of character" is first recorded 1670s. Related: Foibles.
foie gras (n.)
1818, short for pâté de foie gras (see pate (n.2)). Pâté de foie gras (1827 in English) is literally "pie of fat liver;" originally served in a pastry (as still in Alsace), the phrase now chiefly in English with reference to the filling.
foil (v.)
c.1300, foilen "to spoil a trace or scent by running over it," irregularly from Old French fouler "trample," from Vulgar Latin *fullare "to clean cloth" (by treading on it), from Latin fullo "one who cleans cloth, fuller," of unknown origin.

Hence, "to overthrow, defeat" (1540s). Sense of "frustrate the efforts of" first recorded 1560s. Related: Foiled; foiling. Foiled again! as a cry of defeat and dismay is from at least 1847.
foil (n.)
"thin sheet of metal," early 14c., from Old French fueille "leaf," from Latin folia "leaves," plural (mistaken for fem. singular) of folium "leaf" (see folio).

The sense of "one who enhances another by contrast" (1580s) is from the practice of backing a gem with metal foil to make it shine more brilliantly. The meaning "light sword used in fencing" (1590s) could be from this sense, or from foil (v.). The modern sense of "metallic food wrap" is from 1946.
foist (v.)
1540s, from Dutch vuisten "take in hand," from Middle Dutch vuist "fist" (see fist). Earliest sense was cheating at dice by concealing a loaded one in the palm of the hand with the intention of introducing it into play; meaning "introduce surreptitiously" is from 1560s. Related: Foisted; foisting.
Fokker
German monoplane, 1913, from name of A.H.G. Fokker (1890-1939), Dutch engineer and inventor.
fold (v.)
Old English faldan (Mercian), fealdan (West Saxon), transitive, "to bend cloth back over itself," class VII strong verb (past tense feold, past participle fealden), from Proto-Germanic *falthan, *faldan (cognates: Middle Dutch vouden, Dutch vouwen, Old Norse falda, Middle Low German volden, Old High German faldan, German falten, Gothic falþan).

The Germanic words are from PIE *pel-to- (cognates: Sanskrit putah "fold, pocket," Albanian pale "fold," Middle Irish alt "a joint," Lithuanian pleta "I plait"), from root *pel- (3) "to fold" (also source of Greek ploos "fold," Latin -plus).

The weak form developed from 15c. In late Old English also of the arms. Intransitive sense, "become folded" is from c.1300 (of the body or limbs); earlier "give way, fail" (mid-13c.). Sense of "to yield to pressure" is from late 14c. Related: Folded; folding.
fold (n.1)
"pen or enclosure for sheep or other domestic animals," Old English falæd, falud "stall, stable, cattle-pen," a general Germanic word (cognates: East Frisian folt "enclosure, dunghill," Dutch vaalt "dunghill," Danish fold "pen for sheep"), of uncertain origin. Figurative use by mid-14c.
fold (n.2)
"a bend or ply in anything," mid-13c., from fold (v.).
fold-out (n.)
1961, from fold (v.) + out.
folder (n.)
1550s as "one who folds;" 1911 as "folding cover for loose papers;" agent noun from fold (v.).
foliage (n.)
mid-15c., from Middle French feuillage, from Old French feuille "leaf" (see foil (n.)). The form has altered by influence of Latin folium.
foliate (adj.)
1620s, from Latin foliatus "leaved, leafy," from folium (see folio).
foliate (v.)
1660s, "to apply silver leaf," from Latin foliatus "leaved, leafy," from folium (see folio). Meaning "to put forth leaves" is from 1775. Related: Foliated; foliating.
foliation (n.)
1620s, from French foliation or formed in English from Latin foliatus (see foliate (v.)).
folic (adj.)
in reference to type of acid, 1941, coined from Latin folium "leaf" (see folio) + -ic. So called for its abundance in green leaves, such as those of spinach.
folio (n.)
mid-15c., from Late Latin folio "leaf or sheet of paper," from Latin folio, ablative of folium "leaf," from PIE *bhulyom "leaf" (cognates: Greek phyllon "leaf," Gaelic bile "leaflet, blossom"), from root *bhel- (2) "to blow, inflate, swell" (see bole). Ablative of location, because this was used in page references. Meaning "volume of the largest size" first attested 1620s.
folium (n.)
see folio.
folk (n.)
Old English folc "common people, laity; men; people, nation, tribe; multitude; troop, army," from Proto-Germanic *folkom (cognates: Old Frisian folk, Middle Dutch volc, German Volk "people"), from Proto-Germanic *fulka-, perhaps originally "host of warriors;" compare Old Norse folk "people," also "army, detachment;" and Lithuanian pulkas "crowd," Old Church Slavonic pluku "division of an army," both believed to have been borrowed from Proto-Germanic. Old English folcstede could mean both "dwelling-place" and "battlefield."

Some have attempted to link the word to Greek plethos "multitude;" Latin plebs "people, mob," populus "people" or vulgus; OED and Klein discount this theory but it is accepted in Watkins. The plural form has been usual since 17c. Superseded in most senses by people. Old English folc was commonly used in forming compounds, such as folccwide "popular saying," folcgemot "town or district meeting;" folcwoh "deception of the public." Folk-etymology is attested from 1890.
By Folk-etymology is meant the influence exercised upon words, both as to their form and meaning, by the popular use and misuse of them. In a special sense, it is intended to denote the corruption which words undergo, owing either to false ideas about their derivation, or to a mistaken analogy with other words to which they are supposed to be related. [The Rev. A. Smythe Palmer, "Folk-Etymology," 1890]
folk music
1889, from folk (also see folklore). In reference to the branch of modern popular music (originally associated with Greenwich Village in New York City) it dates from 1958.
folkie (n.)
"devotee of (modern) folk music," attested by 1966, with -ie.
folklore (n.)
1846, coined by antiquarian William J. Thoms (1803-1885) as an Anglo-Saxonism (replacing popular antiquities) and first published in the "Athenaeum" of Aug. 22, 1846, from folk + lore. Old English folclar meant "homily."

This word revived folk in a modern sense of "of the common people, whose culture is handed down orally," and opened up a flood of compound formations, as in folk art (1892), folk-hero (1874), folk-medicine (1877), folk-tale/folk tale (1850; Old English folctalu meant "genealogy"), folk-song (1847), folk singer (1876), folk-dance (1877).
folkloric (adj.)
1883, from folklore + -ic.
folklorist (n.)
1881, from folklore + -ist.
folks (n.)
"people of one's family," 1715, colloquial, from plural of folk.