Online Etymology Dictionary

galoot (n.): "awkward or boorish man," 1812, nautical, "raw recruit, green hand," apparently originally a sailor's contemptuous word for soldiers or marines, of uncertain origin. "Dictionary of American Slang" proposes galut, Sierra Leone creole form of Spanish galeoto "galley slave."
galore: 1670s, from Irish go leór, corresponding to Gaelic gu leóir "sufficiently, enough." The particle go/gu usually means "to," but it also is affixed to adjectives to form adverbs, as here.
galoshes (n.): mid-14c., kind of footwear consisting of a wooden sole fastened onto the foot with leather thongs, perhaps from Old French galoche (singular), from Late Latin gallicula, diminutive of gallica (solea) "a Gallic (sandal)" [Klein]. Alternative etymology [Barnhart, Hatz.-Darm.] is from Vulgar Latin *galopia, from Greek kalopodion, diminutive of kalopous "shoemaker's last," from kalon "wood" + pous "foot" (see foot (n.)). The surname Galocher is attested from c.1300. Modern meaning "rubber covering of a boot or shoe" is from 1853.
galumph (v.): "to prance about in a self-satisfied manner," 1872, coined by Lewis Carroll in "Jabberwocky," apparently by blending gallop and triumph. Related: Galumphing.
galvanic (adj.): 1797; see galvanism + -ic.
galvanise (v.): chiefly British English spelling of galvanize; for suffix, see -ize. Related: Galvanised; galvanising.
galvanism (n.): "electricity produced by chemical action," 1797, from French galvanisme or Italian galvanismo, from Italian physicist Luigi Galvani (1737-1798) who discovered it c.1792 while running currents through the legs of dead frogs.
galvanization (n.): 1798, noun of action from galvanize.
galvanize (v.): 1802, from French galvaniser, from galvanisme (see galvanism). Figurative sense of "excite, stimulate (as if by electricity)" first recorded 1853. Meaning "to coat with metal by means of galvanic electricity" (especially to plate iron with tin, but now typically to plate it with zinc) is from 1839.
He'll swear that in her dancing she cuts all others out,
Though like a Gal that's galvanized, she throws her legs about.
[Thomas Hood, "Love has not Eyes," 1845]
Related: Galvanized; galvanizing.
galvanometer (n.): 1802, from comb. form of galvanism + -meter.
gam (n.): "a leg," 1781, see gams.
Gamaliel: masc. proper name, from Greek Gamaliel, from Hebrew Gamli'el, literally "reward of God."
gambit (n.): "chess opening in which a pawn is risked for advantage later," 1650s, gambett, from Italian gambetto, literally "a tripping up" (as a trick in wrestling), from gamba "leg," from Late Latin gamba (see gambol). Applied to chess openings in Spanish in 1561 by Ruy Lopez, who traced it to the Italian word, but the form in Spanish generally was gambito, which led to French gambit, which has influenced the English spelling of the word. Broader sense of "opening move meant to gain advantage" in English is recorded from 1855.
gamble (v.): 1726 (implied in gambling), from a dialectal survival of Middle English gammlen, variant of gamenen "to play, jest, be merry," from Old English gamenian "to play, joke, pun," from gamen (see game). Or possibly gamble is from a derivative of gamel "to play games" (1590s), itself likely a frequentative from game. Originally regarded as a slang word. The intrusive -b- may be from confusion with gambol. Related: Gambled; gambling.
gamble (n.): "risky venture," 1823, from gamble (v.).
gambler (n.): 1747, agent noun from gamble.
gambol (n.): "frolic, merrymaking," 1590s, originally gambolde "a leap or spring" (c.1500), from Middle French gambade (15c.), from Late Latin gamba "horse's hock or leg," from Greek kampe "a bending" (on notion of "a joint"), from PIE *kamp- "to bend" (see campus).
gambol (v.): 1580s; earlier gambade (c.1500), from Middle French gambader, from gambade (see gambol (n.)). Related: Gamboled; gamboling; gambolling.
gambrel (n.): "hipped roof," 1851, short for gambrel roof, so called for its shape, from gambrel "horse's hind leg" (c.1600), earlier "wooden bar to hang carcasses" (1540s), perhaps from Old North French gamberel, from gambe "leg," from Late Latin gamba (see gambol).
game (adj.2): "brave, spirited," 1725, especially in game-cock "bird for fighting," from game (n.). Middle English had gamesome (adj.) "joyful, playful, sportive."
game (n.): Old English gamen "game, joy, fun, amusement," common Germanic (cf. Old Frisian game "joy, glee," Old Norse gaman, Old Saxon, Old High German gaman "sport, merriment," Danish gamen, Swedish gamman "merriment"), regarded as identical with Gothic gaman "participation, communion," from Proto-Germanic *ga- collective prefix + *mann "person," giving a sense of "people together."

Meaning "contest played according to rules" is first attested c.1300. Sense of "wild animals caught for sport" is late 13c.; hence fair game (1825), also gamey. Game plan is 1941, from U.S. football; game show first attested 1961.
game (adj.1): "lame," 1787, from north Midlands dialect, of unknown origin, perhaps a variant of gammy (tramps' slang) "bad," or from Old North French gambe "leg" (see gambol (n.)).
game (v.): Old English gamenian "to play, jest, joke;" see game (n.). Modern usages probably represent recent formations from the noun. Related: Gamed; gaming.
game-cock: 1670s, from game (adj.) in the sporting sense + cock (n.1). Figurative use by 1727.
gamekeeper (n.): 1660s, from game (n.) in the animal sense + agent noun from keep (v.).
gamelan (n.): "East Indian orchestra," 1817, from Javanese gamel "to handle."
gamely (adv.): "courageously," 1861, from game (n.) + -ly (2).
gamer (n.): 1620s, "an athlete," agent noun from game (v.). Meaning "one devoted to playing video or computer games" is attested from 1999. Gamester is attested from 1590s but meant "prostitute" (cf. old slang the first game ever played "copulation"), later "a man fit and ready for anything, a player" (mid-17c.).
gamete (n.): "sexual protoplasmic body," 1880, coined 1878 by German cytologist Eduard Strasburger (1844-1912), the widespread attribution to Mendel being apparently erroneous; from Greek gamete "a wife," gametes "a husband," from gamein "to take to wife, to marry," from PIE root *gem(e)- "to marry" (cf. Greek gambros "son-in-law, father-in-law, brother-in-law;" Sanskrit jamih "brother, sister," jama daughter-in-law;" Avestan zama-tar "son-in-law;" Latin gener "son-in-law"). Cf. also -gamy. The seventh month of the ancient Attic calendar (corresponding to late January and early February) was Gamelion, "Month of Marriages."
gamey (adj.): also gamy, 1844, "spirited, plucky," from game (n.) + -y (2). Meaning "tasting or smelling strongly" is from 1863.
gamin (n.): "street urchin," 1837, from French gamin (18c.), perhaps from Berrichon dialect gamer "to steal." Introduced in English in translations of Hugo.
Un groupe d'enfants, de ces petits sauvages vanu-pieds qui ont de tout temps battu le pavé de Paris sous le nom éternel de gamins, et qui, lorsque nous étions enfants aussi, nous ont jeté des pierres à tous, le soir, au sortir de classe, parce que nos pantalons n'étaient pas déchirés; etc. [Hugo, "Notre-Dame de Paris"]
gamine (n.): "small, slim, pert young girl," 1899, from French gamine, fem. of gamin.
gaming (n.): c.1500, "gambling," verbal noun from present participle of game (v.).
gamma: third letter of the Greek alphabet, c.1400, from Greek gamma, from Phoenician gimel, literally "camel" (see camel); so called for a fancied resemblance of its shape to some part of a camel. Gamma rays (1903) originally were thought to be a third type of radiation, now known to be identical with very short X-rays.
gammadion (n.): swastika-like figure formed of four capital gammas, Medieval Greek gammadion, diminutive of Greek gamma (see gamma).
gammer (n.): "old woman," 1570s, contraction of grandmother (cf. gaffer).
gammon (n.): early 15c., "ham or haunch of a swine," from Old North French gambon "ham" (French jambon), from gambe "leg," from Late Latin gamba "leg of an animal" (see gambol (n.)).
gams (n.): "legs," 1781, low slang, probably the same word as gamb "leg of an animal on a coat of arms" (1727) and ultimately from Middle English gamb "leg," from Old North French (see gammon). Now, in American English slang, especially with reference to well-formed legs of pretty women, but this was not the original sense.
gamut (n.): 1520s, originally, "lowest note in the medieval musical scale," in the system of notation devised by Guido d'Arezzo, contraction of Medieval Latin gamma ut, from gamma, the Greek letter, indicating a note below A, + ut (later do), the low note on the six-note musical scale that took names from corresponding syllables in a Latin hymn for St. John the Baptist's Day:
Ut queant laxis resonare fibris
Mira gestorum famuli tuorum
Solve polluti labii reatum,
etc. Gamut came to be used for "the whole musical scale;" the figurative sense of "entire scale or range" of anything is first recorded 1620s.
gamy (adj.): see gamey.
ganch (v.): "to impale on hooks or pointed stakes as a means of capital punishment," 1610s, from French *ganchor, from Italian *ganciare, from gancio "hook," from Turkish kanca "hook, barb, grapnel." Related: Ganched; ganching. Also, as a noun, the name of the thing used in killing.
gander (v.): "take a long look," slang, 1886, from gander (n.) on the notion of craning one's neck like a goose; earlier it meant "to wander foolishly" (1680s). Related: Gandered; gandering.
gander (n.): Old English gandra "male goose," from Proto-Germanic *gan(d)ron- (cf. Dutch gander, Middle Low German ganre), from PIE *ghans- "goose" (see goose (n.)). OED suggests perhaps originally the name of some other water-bird and cites Lithuanian gandras "stork." Sometimes used 19c. like stag in reference to single men or male-only gatherings. Meaning "a long look" is 1912, from gander (v.).
gandy dancer: "railroad maintenance worker," 1918, American English slang, of unknown origin; dancer perhaps from movements required in the work of tamping down ties or pumping a hand-cart, gandy perhaps from the name of a machinery belt company in Baltimore, Maryland.
gang (v.): 1856, from gang (n.). Related: Ganged; ganging. To gang up (on) is first attested 1919.
gang (n.): from Old English gang "a going, journey, way, passage," and Old Norse gangr "a group of men, a set," both from Proto-Germanic *gangaz (cf. Old Saxon, Old Frisian, Danish, Dutch, Old High German, German gang, Old Norse gangr, Gothic gagg "act of going"), from PIE root *ghengh- "to step" (cf. Sanskrit jangha "shank," Avestan zanga- "ankle," Lithuanian zengiu "I stride"). Thus not considered to be related to go.

The sense evolution is probably via meaning "a set of articles that usually are taken together in going" (mid-14c.), especially a set of tools used on the same job. By 1620s this had been extended in nautical speech to mean "a company of workmen," and by 1630s the word was being used, with disapproving overtones, for "any band of persons traveling together." Gangway preserves the original sense of the word, as does gangplank.
Gang of Four: 1976, translating Chinese sirenbang, the nickname given to the four leaders of the Cultural Revolution who took the fall in Communist China after the death of Mao.
gang-bang (n.): 1953, "group sex" (especially many men on one woman or girl, regardless of consent), from gang + bang with slang meaning "do the sex act." Earlier was gang-shag (1927). Sense of "participate in a street gang" is by 1968. Related: Gang-banger; gang-banging.
gangbusters (n.): to come on like gangbusters (c.1940) is from U.S. radio crimefighting drama "Gangbusters" (1937-57) which opened with a cacophony of sirens, screams, shots, and jarring music.
Ganges: from Sanskrit ganga "current, river."