Online Etymology Dictionary

-gate: suffix attached to anything to indicate "scandal involving," 1973, abstracted from Watergate, Washington, D.C., building complex, home of the National Headquarters of the Democratic Party when it was burglarized June 17, 1972.
-gram: suffix from telegram (1857), first abstracted 1979 (in Gorillagram, a proprietary name in U.S.), and put to wide use in forming new words, such as stripagram (1981). The construction violates Gk. grammar, as an adv. could not properly form part of a compound noun.
g spot: 1981, short for Gräfenberg spot, named for German gynecologist Ernst Gräfenberg, who described it in 1950.
G-man: "FBI agent," 1930, shortening of government man; used earlier in an Irish context (1917), but the abbreviation is perhaps the same one.
G-string: 1878, geestring, "loincloth worn by American Indian," originally the string that holds it up, etymology unknown. The spelling with G (1891) is perhaps from influence of violin string tuned to a G (in this sense G string is first recorded 1831). First used of women's attire 1936, with reference to strip-teasers.
G.I.: 1936 (adj.), Amer.Eng., apparently an abbreviation of Government Issue, applied to anything associated with servicemen. Transferred sense to "soldiers" during World War II (first recorded 1943) is from the jocular notion that the men themselves were manufactured by the government. An earlier G.I. was an abbreviation of Galvanized Iron in G.I. can, a type of metal trash can, the term being picked up by U.S. soldiers in World War I as slang for a similar-looking type of German artillery shells. This use is attested from 1928, but it is highly unlikely that this came to mean "soldier." I probably get more e-mail about this entry than any other. No two sources I have agree on the etymology, but none backs the widespread notion that it stands for *General Infantry.
gab: c.1200, via Scottish and northern England dialect, from O.N. gabba "to mock," or O.Fr. gabber "mock, boast," both probably ultimately imitative. Gabby first attested 1719; gabfest "session of conversation" is 1897 Amer.Eng. slang. Gift of the gab "talent for speaking" is from 1680s.
gabardine: 1590s, "dress, covering," variant of gaberdine. Meaning "closely woven cloth" is from 1904.
gabble: 1570s, frequentative of gab (q.v.).
gabbro: "type of igneous rock," 1837, from It. (Tuscan), from L. glaber "bare, smooth, bald."
gabby: "garrulous, talkative," 1710, originally Scottish, from gab + -y (2).
Gabe: masc. proper name, usually short for Gabriel.
gaberdine: "long, loose outer garment," 1510s, from Sp. gabardina, from M.Fr. galverdine, which is perhaps from M.H.G. wallevart "pilgrimage," in the sense of "pilgrim's cloak." The Spanish form perhaps influenced by gabán "overcoat" and tabardina "coarse coat."
gable: mid-14c., from O.Fr. gable, from O.N. gafl (in north of England, directly from O.N.), probably from a P.Gmc. root meaning "fork" (cf. O.E. gafol, geafel "fork," M.H.G. gabel "pitchfork"), from PIE *ghebhel (cf. O.Ir. gabul "forked twig"). So called from the Y-shaped timber supports of the roof at gable ends. Related: Gabled; gables.
Gabriel: name of an archangel in O.T., from Heb. Gabhri el, lit. "man of God," from gebher "man" + El "God." First element is from base of verb gabhar "was strong" (cf. Arabic jabr "strong, young man;" jabbar "tyrant").
gad (v.): "to rove about," mid-15c., perhaps a back-formation of O.E. gædeling "wandering," or associated with gad (n.) "a goad for driving cattle" (see gadfly). Related: Gadding.
gadabout (n.): 1837, from earlier noun phrase gadder about (1560s); see gad (v.) + about.
gadfly (n.): 1620s, "fly which bites cattle," probably from gad "goad, metal rod" (early 13c.), here in the sense of "stinger," from O.N. gaddr "spike, nail," from P.Gmc. *gadaz "pointed stick;" but sense is entangled with gad (v.) and an early meaning of gadfly was also "someone who likes to go about, often stopping here and there." Sense of "one who irritates another" is from 1640s (equivalent of L. oestrus).
gadget: 1886, gadjet (but said to date back to 1850s), sailors' slang word for any small mechanical thing or part of a ship for which they lacked, or forgot, a name; perhaps from Fr. gâchette "catchpiece of a mechanism," dim. of gâche "staple of a lock."
gadzooks: 1690s, from some exclamation, possibly God's hooks (nails of the cross) or even God's hocks. The use of Gad for God (cf. egad) is first attested 1590s. Among other similar phraseological combinations (all from 17c.) were gadsbobs, gadslid, and gadsniggers.
Gaea: see Gaia.
Gael: 1810, from Scottish Gaelic Gaidheal "member of the Gaelic race," from O.Ir. Goidhel. The native name in both Ireland and Scotland, Gael was first used in English exclusively of Scottish Highlanders.
Gaelic: 1774, earlier Gathelik (1590s), from Gael (Scottish Gaidheal); see Gael.
gaff (1): "iron hook," 1725, gaffe, from Fr. gaffe "boat hook" (see gaffe). Specifically of the hook on a fishing spear from 1650s.
gaff (2): "loud, rude talk," 1825, from Scottish dialect, perhaps a survival of O.E. gafspraec "blasphemous or ribald speech," or from gaff (1), and cf. gaffe.
gaffe: "blunder," 1909, perhaps from Fr. gaffe "clumsy remark," originally "boat hook," from O.Fr. gaffe, from O.Prov. gaf, probably from W.Goth. *gafa "hook," from P.Gmc. *gafa. Sense connection is obscure. The gaff was also used to land big fish. Or it may derive from Brit. slang gaff "to cheat, trick" (1893); or gaff "criticism" (1896), from Scot. dial. sense of "loud, rude talk," which ultimately may be from O.E. gaf-spræc "blasphemous or ribald speech."
gaffer: 1589, "elderly rustic," apparently a contraction of godfather; originally "old man," it was applied from 1841 to foremen and supervisors, which sense carried over 20c. to "electrician in charge of lighting on a film set."
gag (v.): mid-15c., "to choke, strangle," possibly imitative or influenced by O.N. gaghals "with head thrown back." The sense of "stop a person's mouth" is first attested c.1500. Related: Gagged; gagging. The noun is 1550s, from the verb.
gag (n.): "joke," 1823, probably related to theatrical sense of "matter interpolated in a written piece by the actor" (1847), or from slang verbal sense of "to deceive, take in with talk" (1777), both on notion of "stuff, fill" (see gag (v.)).
gaga: "crazy, silly," 1905, probably from Fr. gaga "senile, foolish."
gage (n.): "pledge," c.1300, from O.Fr. gage, from Frank. *wadja-, related to Goth. wadi "pledge," from P.Gmc. *wadjon (see wed).
gage (v.): see gauge. "The spelling variants gauge and gage have existed since the first recorded uses in Middle English, though in American English gage is found exclusively in technical uses" [Barnhart]. Related: Gaged; gaging.
gaggle: late 15c., gagyll, with reference to both geese and women. Barnhardt says possibly from O.N. gagl "goose;" OED calls it "one of the many artificial terms invented in the 15th c. as distinctive collectives referring to particular animals or classes of persons." Possibly of imitative origin (cf. Du. gagelen "to chatter;" M.E. gaggle "to cackle," used of geese, attested from late 14c.).
Gaia: "Earth as a goddess," from Gk. Gaia, personification of gaia "earth," a collateral form of ge (Dorian ga) "earth," of unknown origin. The Roman equivalent goddess of the earth was Tellus (see tellurian), sometimes used in Eng. poetically or rhetorically for "Earth personified" or "the Earth as a planet."
gaiety: 1640s, from Fr. gaieté, from gai "gay" (see gay).
gaily: late 14c., from M.E. gai (see gay) + -ly (2).
gain: late 15c. (n.), 1520s (v.), from M.Fr. gain, from O.Fr. gaaigne, from gaaignier "to gain," also "cultivate land," from Frank. *waidanjan "hunt, forage," also "graze, pasture," from P.Gmc. *wartho "hunting ground" (cf. Ger. weide "pasture, pasturage," O.N. veiðr "hunting"), from PIE *wei "to strive after." The original O.Fr. sense enfolded the notions of "profit from agriculture" and "booty, prey." Related: Gained; gaining.
gainful: 1540s (implied in gainfully), from gain + -ful.
gainsay: "to contradict," c.1300, lit. "say against," from O.E. gegn- "against" + say. "Solitary survival of a once common prefix" [Weekley], which was used to form such now-obsolete compounds as gain-taking "taking back again," gainclap "a counterstroke," gainbuy "redeem," and gainstand "to oppose." Related: Gainsaid; gainsaying.
gait: c.1200, gate "a going or walking, departure, journey," earlier "way, road, path," from O.N. gata "way, road, path." Meaning "manner of walking" is from 1509. Modern spelling developed before 1750, originally in Scottish.
gaiter: "leather cover for the ankle," 1775, perhaps from Fr. guêtre "belonging to peasant attire," from M.Fr. *guestre, probably from Frank. *wrist "instep," from P.Gmc. *wirstiz from *wrig-, *wreik- "to turn" (see wry). Related: Gaiters.
gal: slang pronunciation of girl, 1795, execrated as a Cockney vulgarism. Gal Friday is 1940, in reference to "Robinson Crusoe."
gala: 1625, "festive dress or attire," from Fr. en gala, from It. gala (as in phrase vestido de gala "robe of state"), perhaps from Arabic khil'a "fine garment given as a presentation." Sense of "festive occasion" (characterized by display of finery) first recorded 1777.
galactic: 1839, from L.L. galacticus, from galaxias (see galaxy).
Galapagos: islands named for the tortoises (Sp. galapagos) who live there; discovered by Europeans in 1535.
galavant: variant of gallivant. Related: Galavanting.
galaxy: late 14c., from L.L. galaxias "Milky Way," from Gk. galaxis (adj.), from gala (gen. galaktos) "milk" (see lactation). The technical astronomical sense emerged 1848. Fig. sense of "brilliant assembly of persons" is from 1580s. Milky Way is a translation of L. via lactea.
"See yonder, lo, the Galaxyë Which men clepeth the Milky Wey, For hit is whyt." [Chaucer, "House of Fame"]
Galbraith: surname, from O.Gael. Gall-Bhreathnach "stranger-Briton," a name given to Britons settled among Gaels.
gale: "storm at sea," 1540s, from gaile "wind," origin uncertain, perhaps from O.N. gol "breeze," or O.Dan. gal "bad, furious" (often used of weather), from O.N. galinn "bewitched." Or perhaps it is from O.E. galan "to sing" (the second element in nightingale), or giellan "to yell." In technical meteorological use, a wind between 32 and 63 miles per hour.
Galilee: "northernmost province of Palestine," late 12c., from L. Galilaea, Gk. Galilaia, from Heb. Haggalil, lit. "The District," a compressed form of Gelil haggoyim "the District of Nations" (cf. Isa. viii:23). The adj. Galilean is used both of Christ (1630s), who was born there, and of the It. astronomer Galileo (1727) who so shook the Christian Church.