Online Etymology Dictionary

fog (v.): 1590s (transitive), from fog (n.1). Intransitive use from 1849. Related: Fogged; fogging.
fog-horn (n.): 1844, from fog (n.1) + horn (n.).
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 (1772) "old-fashioned," also "old-fashioned person;" or from fog (n.2) in an obsolete senses of "moss," or from foggy "bloated, fat" (1520s), which perhaps is an extended sense of fog (n.2). Related: Fogeydom; fogeyish; fogeyism.
foggy (adj.): 1540s, of the air, "full of thick mist," perhaps from a Scandinavian source, or formed from fog (n.1) + -y (2). Foggy Bottom "U.S. Department of State," is 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."
foible (n.): 1640s, "weak point of a sword blade" (contrasted to forte), from French foible "a weak point, a weakness, failing," from noun use of Old French adjective feble "feeble" (see feeble). The spelling borrowed in English is obsolete in modern French, which uses faible. Extended sense of "weak point of character" is first recorded 1670s. Related: Foibles.
foie-gras (n.): 1818, French, short for pâté de foie gras (1827 in English), 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. French foie "liver" is cognate with Italian fegato, from Latin *ficatum. For pâté see pate (n.2); for gras see grease (n.).
foil (v.1): c. 1300, foilen "to spoil a trace or scent by running over it" (more commonly defoilen), irregularly from Old French foler, fuler "trample on, injure, maim; ill-treat, deceive, get the better of" (13c., Modern French fouler), from Vulgar Latin *fullare "to clean cloth" (by treading on it), from Latin fullo "one who cleans cloth, a fuller," which is of unknown origin. Compare full (v.).

Hence, "to overthrow, defeat" (1540s; as a noun in this sense from late 15c.); "frustrate the efforts of" (1560s). Related: Foiled; foiling. Foiled again! as a cry of defeat and dismay is from at least 1847.
foil (n.): "very thin sheet of metal," early 14c., foile, from Old French foil, fueill, fueille "leaf; foliage; sheet of paper; sheet of metal" (12c., Modern French fueille), from Latin folia, 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 sense of "metallic food wrap" is from 1897.
foil (v.2): "apply foil to," 1610s, from foil (n.1).
foist (v.): 1540s, probably from Dutch vuisten "take in hand," from Middle Dutch vuist "fist" (see fist (n.)). 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; general meaning "introduce surreptitiously, work in by a trick" is from 1560s. Related: Foisted; foisting.
Fokker (n.): German monoplane of World War I, 1913, from name of Anton "Anthony" H.G. Fokker (1890-1939), Dutch engineer and inventor who started his aircraft manufacturing business in Germany in 1912.
fold (v.): Old English faldan (Mercian), fealdan (West Saxon), transitive, "to bend (cloth) back over itself, wrap up, furl," class VII strong verb (past tense feold, past participle fealden), from Proto-Germanic *falthan, *faldan (source also of 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- (source also of 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).

Of the arms, from late Old English. Intransitive sense "become doubled upon itself" is from c. 1300 (of the body); earlier "give way, fail" (mid-13c.). Sense of "to yield to pressure" is from late 14c. The weak conjugation developed from 15c. 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.). Compare similarly formed Middle Dutch voude, Dutch vouw, Old High German falt, German Falte, Old Norse faldr.
fold-out (n.): larger page, inserted folded, in a book, magazine, etc., 1961, from fold (v.) + out (adv.).
folder (n.): 1550s, "one who folds;" 1903, "folding cover for loose papers" (earlier as "a fold-up document," often a railway timetable or map); agent noun from fold (v.).
foliage (n.): mid-15c., "representation of leaves or branches" (as an ornamental design), from Middle French feuillage, from Old French feuille "leaf, foliage" (see foil (n.)). The form has altered 17c. by influence of Latin folium or its derivatives in English.
foliate (adj.): 1620s, "beaten into thin sheets," from Medieval Latin foliatus "leaved, leafy," from Latin folium "a leaf" (see folio). As "leaf-like" from 1650s.
foliate (v.): 1660s (implied in foliated), "to apply silver leaf," from Medieval Latin foliatus "leaved, leafy," from Latin folium "a leaf" (see folio). Meaning "put forth leaves" is from 1775. Related: Foliated; foliating.
foliation (n.): 1620s, from Latin foliat-, stem of folium "a leaf" (see folio).
folic (adj.): 1941, in folic acid, coined from Latin folium "a 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" (source also of Italian foglia, French feuille, Spanish hoja), from PIE *bhol-yo- "leaf" (source also of Greek phyllon "leaf," Gaelic bile "leaflet, blossom"), suffixed form of root *bhel- (3) "to thrive, bloom," which is possibly from *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 *folkam (source also of Old Saxon folc, Old Frisian folk, Middle Dutch volc, Dutch volk, Old High German folc, German Volk "people"). 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." According to Watkins, from PIE *ple-go-, suffixed form of root *pele- (1) "to fill," which would make it cognate with Greek plethos "people, multitude." Superseded in most senses by people. Generally a collective noun in Middle English, however plural folks is attested from 15c.

Old English folc was commonly used in forming compounds (59 are listed in the Clark Hall dictionary), such as folccwide "popular saying," folcgemot "town or district meeting;" folcwoh "deception of the public." Modern use of folk as an adjective is from c. 1850 (see folklore).
folk-etymology (n.): 1882; see folk (n.) + etymology.
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," 1882]
folk-music (n.): "music of the people," 1852 (Andrew Hamilton, "Sixteen Months in the Danish Isles"), from folk in the "of the people" sense (also see folklore) + music. Modeled on German Volksmusik. In reference to a branch of modern popular music imitative of the simple and artless style of music originating among the common people (originally associated with Greenwich Village in New York City) it dates from 1958.
Of airs properly national, it should be remembered, the composers are not known. They are found existing among the people, who are ignorant of their origin. They are, to borrow a German phrase, folk-music. [Richard Grant White, "National Hymns," New York, 1861]

The term National Music implies that music, which, appertaining to a nation or tribe, whose individual emotions and passions it expresses, exhibits certain peculiarities more or less characteristic, which distinguish it from the music of any other nation or tribe.*
* The Germans call it Volksmusik, a designation which is very appropriate, and which I should have rendered folk-music, had this word been admissible. [Carl Engel, "An Introduction to the Study of National Music," London, 1866]
folkie (n.): "devotee of (modern) folk music," attested by 1966; with -ie.
folklore (n.): "traditional beliefs and customs of the common people," 1846, coined by antiquarian William J. Thoms (1803-1885) as an Anglo-Saxonism (replacing popular antiquities) in imitation of German compounds in Volk- and first published in the "Athenaeum" of Aug. 22, 1846; see 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: Folk art (1892), folk-hero (1874), folk-medicine (1877), folk-tale (1850; Old English folctalu meant "genealogy"), folk-song (1847, "a song of the people," translating German Volkslied), folk-singer (1876), folk-dance (1877).
folkloric (adj.): 1883, from folklore + -ic.
folklorist (n.): also folk-lorist, "one engaged in the study of folklore," 1881, from folklore + -ist.
folks (n.): "persons," Middle English, plural of folk (n.). Colloquial sense of "people of one's family" is from 1715. In Old English in plural use it meant only "peoples, nations."
folksy (adj.): "sociable, unpretentious," 1852, U.S. colloquial, from folks + -y (2). Related: Folksiness.
folkways (n.): coined 1906 in a book of the same name by U.S. sociologist William Graham Sumner (1840-1910); see folk (n.) + way (n.).
Folkways are habits of the individual and customs of the society which arise from efforts to satisfy needs. ... Then they become regulative for succeeding generations and take on the character of a social force. [Sumner, "Folkways"]
Sumner also often is credited with ethnocentrism, which is found in the same book but is older.
folky (adj.): "characteristic of the common people," 1914, from folk + -y (2). Old English had folcisc "popular, secular, common."
follicle (n.): early 15c., in anatomy, "small sack," from Latin folliculus "a little bag," diminutive of follis "bellows, inflated ball, money-bag," from PIE *bhol-n-, suffixed form of root *bhel- (2) "to blow, swell" (see bole). Related: Follicular.
follies (n.): "glamorous theatrical revue with lots of pretty girls," 1880, from French folies (mid-19c.), from folie (see folly), probably in its sense of "extravagance" (compare extravaganza).
follow (v.): Middle English folwen, from Old English folgian, fylgian, fylgan "to accompany (especially as a disciple), move in the same direction as; follow after, pursue, move behind in the same direction," also "obey (a rule or law), conform to, act in accordance with; apply oneself to (a practice, trade, or calling)," from Proto-Germanic *fulg- (source also of Old Saxon folgon, Old Frisian folgia, Middle Dutch volghen, Dutch volgen, Old High German folgen, German folgen, Old Norse fylgja "to follow"). Probably originally a compound, *full-gan, with a sense of "full-going," the sense then shifting to "serve, go with as an attendant" (compare fulfill). Related: Followed; following.

Sense of "accept as leader or guide, obey or be subservient to" was in late Old English. Meaning "come after in time" is from c. 1200; meaning "to result from" (as effect from cause) is from c. 1200. Meaning "to keep up with mentally, comprehend" is from 1690s. Intransitive sense "come or go behind" is from mid-13c. To follow one's nose "go straight on" first attested 1590s. "The full phrase is, 'Follow your nose, and you are sure to go straight.' " [Farmer]. The children's game follow my leader is attested by that name from 1812 (as follow the leader by 1896).
follow-through (n.): 1896, of golf swings, from verbal phrase follow through; see follow (v.) + through (adv.). Figurative use from 1926.
follow-up (n.): 1905, originally in the argot of sales and business, from verbal phrase follow up "pursue closely, act on energetically" (1794); see follow (v.) + up (adv.).
follower (n.): Old English folgere "retainer, servant, disciple; successor," agent noun from follow. Compare similarly formed Old Frisian folgere, Dutch volger, German Folger. Related: Followers.
following (n.): late 14c., "action of following, an act of following," verbal noun from follow (v.). Meaning "a body of disciples or retainers" is from mid-15c.; Old English used folgoð in this sense.
folly (n.): early 13c., "mental weakness; foolish behavior or character; unwise conduct" (in Middle English including wickedness, lewdness, madness), from Old French folie "folly, madness, stupidity" (12c.), from fol (see fool (n.)). From c. 1300 as "an example of foolishness;" sense of "costly structure considered to have shown folly in the builder" is attested from 1650s. But used much earlier, since Middle English, in place names, especially country estates, probably as a form of Old French folie in its meaning "delight." Related: Follies.
Fomalhaut: bright star in the constellation Piscis Austrinus, 1594, from Arabic Fum al Hut "the Fish's Mouth," which describes its position in the imaginary star-picture.
foment (v.): early 15c., "apply hot liquids," from Old French fomenter "apply hot compress (to a wound)" (13c.), from Late Latin fomentare, from Latin fomentum "warm application, poultice," contraction of *fovimentum, from fovere "to warm; cherish, encourage" (see fever). Extended sense of "stimulate, instigate" (1620s), on the notion of "encourage the growth of," as if by heat, probably was taken from French. Related: Fomented; fomenting.
fomentation (n.): c. 1400, from Late Latin fomentationem (nominative fomentatio), noun of action from past participle stem of fomentare "to foment," from Latin fomentum (see foment).
Fomorian (adj.): pertaining to the monstrous race in Irish mythology, 1876, from Irish fomor "pirate, monster," from fo "under" + mor "sea." Cognate with Gaelic famhair.
fond (adj.): late 14c., "deranged, insane;" also "foolish, silly, unwise," from fonned, past participle adjective from obsolete verb fon, fonne (Middle English fonnen) "be foolish, be simple," from Middle English fonne "a fool, stupid person" (early 14c.), which is of uncertain origin but perhaps from Scandinavian. Related: Fonder; fondest.

Meaning evolved via "foolishly tender" to "having strong affections for" (by 1570s). Another sense of the verb fon was "to lose savor" (late 14c. in Middle English past participle fonnyd), which may be the original meaning of the word:
Gif þe salt be fonnyd it is not worþi [Wyclif, Matt. v:13, c. 1380]
fondant (n.): 1877, from French fondant, noun use of present participle of fondre "to melt" (see found (v.2)).
fondle (v.): 1690s, "treat with indulgence and affection" (now obsolete), from fond (adj.) + frequentative ending. Or possibly from the obsolete verb fond "be fond, be in love, dote" (1520s), from the adjective or altered from earlier fon. Sense of "caress" first recorded 1796. As a noun from 1833. Related: Fondled; fondling (1670s as a past participle adjective); fondlesome.