Guelph
one of the two great parties in medieval Italian politics, characterized by support of the popes against the emperors (opposed to the Ghibellines), 1570s, from Italian Guelfo, from Old High German Welf, name of a princely family that became the ducal house of Brunswick, literally "whelp," originally the name of the founder. The family are the ancestors of the present dynasty of Great Britain. The name is said to have been used as a war-cry at the Battle of Weinsberg (1140) by partisans of Henry the Lion, duke of Bavaria, who was of the family, against Emperor Conrad III; hence it was adopted in Italy as the name of the anti-imperial party.
guerdon (n.)
"reward, recompense" (now only poetic), late 14c., from Old French guerdon, guerredon "reward, recompense, payment," from Medieval Latin widerdonum, from Old High German widarlon "recompense;" compare Old English wiðerlean "requital, compensation," from wiðer "again" (see with) + lean "payment." Form influenced in Medieval Latin by Latin donum "gift." Compare Spanish galardon, Italian guiderone.
guerilla (n.)
variant of guerrilla (q.v.); compare French guérilla.
Guernsey
breed of cattle, 1834, from the Channel Island where it was bred; the island name is Viking. Like neighboring Jersey, it was also taken as the name for a coarse, close-fitting vest of wool (1839), and in Australia the word supplies many of the usages of jersey in U.S. The second element of the name is Old Norse ey "island;" the first element uncertain, traditionally meaning "green," but perhaps rather representing a Viking personal name, such as Grani.
guerrilla (n.)
"fighter in an irregular, independent armed force," 1809, from Spanish guerrilla "body of skirmishers, skirmishing warfare," literally "little war," diminutive of guerra "war," from a Germanic source (cognate with Old High German werra "strife, conflict, war;" see war (n.)). Figurative use by 1861. As an adjective from 1811. Acquired by English during the Peninsular War (1808-1814); purists failed in their attempt to keep this word restricted to "irregular warfare" and prevent it taking on the sense properly belonging to guerrillero "guerrilla fighter."
guess (v.)
c.1300, gessen "to estimate, appraise," originally "take aim," probably from Scandinavian (compare Middle Danish gitse, getze "to guess," Old Norse geta "guess, get"), possibly influenced by Middle Dutch gessen, Middle Low German gissen "to guess," all from Proto-Germanic *getiskanan "to get" (see get). Sense evolution is from "to get," to "to take aim at," to "to estimate." Meaning "to hit upon the right answer" is from 1540s. U.S. sense of "calculate, recon" is true to the oldest English meaning. Spelling with gu- is late 16c., sometimes attributed to Caxton and his early experience as a printer in Bruges. Related: Guessed; guessing. Guessing game attested from 1650s.
guess (n.)
c.1300, from guess (v.). Verbal shrug phrase your guess is as good as mine attested from 1902.
guesstimate (v.)
1902, a blending of guess (v.) and estimate. Related: Guesstimated; guesstimating. As a noun, from 1906.
guesswork (n.)
also guess-work, 1725, from guess + work (n.).
guest (n.)
Old English gæst, giest (Anglian gest) "guest; enemy; stranger," the common notion being "stranger," from Proto-Germanic *gastiz (cognates: Old Frisian jest, Dutch gast, German Gast, Gothic gasts "guest," originally "stranger"), from PIE root *ghos-ti- "stranger, guest; host" (cognates: Latin hostis "enemy," hospes "host" -- from *hosti-potis "host, guest," originally "lord of strangers" -- Greek xenos "guest, host, stranger;" Old Church Slavonic gosti "guest, friend," gospodi "lord, master"); the root sense, according to Watkins, probably is "someone with whom one has reciprocal duties of hospitality," representing "a mutual exchange relationship highly important to ancient Indo-European society." But as strangers are potential enemies as well as guests, the word has a forked path.

Spelling evolution influenced by Old Norse cognate gestr (the usual sound changes from the Old English word would have yielded Modern English *yest). Phrase be my guest in the sense of "go right ahead" first recorded 1955.
guest star (n.)
1914 in the entertainment sense; earlier the phrase was used literally, of novae. As a verb, by 1942.
guestroom (n.)
also guest-room, 1630s, from guest (n.) + room (n.). Guest chamber is recorded from 1520s.
guff (n.)
"empty talk, nonsense," 1888, from earlier sense of "puff of air" (1825), of imitative origin.
guffaw (n.)
1720, Scottish, probably imitative of the sound of coarse laughter. Compare gawf (early 16c.) "loud, noisy laugh." The verb is from 1721. Related: Guffawed; guffawing.
Guggenheim
grant for advanced study, in reference to the John Simon Guggenheim Foundation, established 1925 by U.S. Sen. Simon Guggenheim (1867-1941) in memory of his son, who died young. The senator's brother was an arts patron who founded the Solomon R. Guggenheim Foundation in 1937, which grew into the Guggenheim Museum of modern art.
guidance (n.)
1530s, "the process of directing conduct," hybrid from guide + -ance; replacing 15c. guying. In reference to direction in school, career, marriage, etc., from 1927.
guide (v.)
late 14c., "to lead, direct, conduct," from Old French guider "to guide, lead, conduct" (14c.), earlier guier, from Frankish *witan "show the way" or a similar Germanic source, from Proto-Germanic *wit- "to know" (cognates: German weisen "to show, point out," Old English witan "to see"), from PIE *weid- "to see" (see vision). The form of the French word influenced by Old Provençal guidar (n.) "guide, leader," or Italian guidare, both from the same source. Related: Guided; guiding.
guide (n.)
mid-14c., "one who shows the way," from Old French guide, 14c. (alteration of earlier guie), verbal noun from guider (see guide (v.)). In book titles from 1610s; meaning "book of information on local sites" is from 1759. In 18c. France, a "for Dummies" or "Idiot's Guide to" book would have been a guid' âne, literally "guide-ass."
guideline (n.)
1785, "line marked on a surface before cutting," from guide + line (n.). Meaning "rope for steering a hot-air balloon" is from 1846. In figurative use by 1948. Related: Guidelines.
guidepost (n.)
also guide-post, 1761, from guide (v.) + post (n.1).
Guido
masc. proper name, Italian, literally "leader," of Germanic origin (see guide (v.)). As a type of gaudy machoism often associated with Italian-Americans, 1980s, teen slang, from the name of character in Hollywood film "Risky Business" (1983).
guidon (n.)
"small flag," 1540s, from Middle French guidon (16c.), from Italian guidone "battle standard," from guidare "to direct, guide," from Old Provençal guidar (see guide (v.)).
guild (n.)
early 13c., yilde (spelling later influenced by Old Norse gildi "guild, brotherhood"), a semantic fusion of Old English gegyld "guild" and gild, gyld "payment, tribute, compensation," from Proto-Germanic *gelth- "pay" (cognates: Old Frisian geld "money," Old Saxon geld "payment, sacrifice, reward," Old High German gelt "payment, tribute;" see yield (v.)).

The connecting sense is of a tribute or payment to join a protective or trade society. But some see the root in its alternative sense of "sacrifice," as if in worship, and see the word as meaning a combination for religious purposes, either Christian or pagan. The Anglo-Saxon guilds had a strong religious component; they were burial societies that paid for masses for the souls of deceased members as well as paying fines in cases of justified crime. The continental custom of guilds of merchants arrived after the Conquest, with incorporated societies of merchants in each town or city holding exclusive rights of doing business there. In many cases they became the governing body of a town (compare Guildhall, which came to be the London city hall). Trade guilds arose 14c., as craftsmen united to protect their common interest.
guilder (n.)
Dutch coin, late 15c., probably from a mispronunciation of Middle Dutch gulden, literally "golden," in gulden (florijn) or some similar name for a golden coin (see golden).
guile (n.)
mid-12c., from Old French guile "deceit, wile, fraud, ruse, trickery," from Frankish *wigila "trick, ruse" or a related Germanic source (cognates: Old Frisian wigila "sorcery, witchcraft," Old English wil "trick;" see wile).
guileful (adj.)
c.1300, from guile + -ful. Nowadays only in poems and dictionaries. Related: Guilefully; guilefulness.
guileless (adj.)
1727, from guile + -less. Related: Guilelessly; guilelessness.
guillotine (n.)
"The name of the machine in which the axe descends in grooves from a considerable height so that the stroke is certain and the head instantly severed from the body." ["Universal Magazine of Knowledge and Pleasure," January 1793], 1791, from French guillotine, named in recognition of French physician Joseph Guillotin (1738-1814), who as deputy to the National Assembly (1789) proposed, for humanitarian and efficiency reasons, that capital punishment be carried out by beheading quickly and cleanly on a machine, which was built in 1791 and first used the next year. The verb is first attested 1794. Related: Guillotined; guillotining.
guilt (n.)
Old English gylt "crime, sin, fault, fine," of unknown origin, though some suspect a connection to Old English gieldan "to pay for, debt," but OED editors find this "inadmissible phonologically." The mistaken use for "sense of guilt" is first recorded 1680s. Guilt by association recorded by 1919.
guilt (v.)
"to influence someone by appealing to his sense of guiltiness," by 1995, from guilt (n.). Related: Guilted; guilting. Old English also had a verbal form, gyltan "to commit an offense."
guiltiness (n.)
late 14c., from guilty + -ness.
guiltless (adj.)
late Old English gyltleas; see guilt (n.) + -less. Related: Guiltlessly; guiltlessness.
guilty (adj.)
Old English gyltig, from gylt (see guilt (n.)). Of conscience, feelings, etc., 1590s. Meaning "person who is guilty" is from 1540s. To plead not guilty is from 15c.; to plead guilty is 19c., though, as OED notes, "Guilty is technically not a plea, but a confession."
guinea (n.)
former British coin, 1660s, from Guinea, region along the west coast of Africa, presumably from an African word (perhaps Tuareg aginaw "black people"); the 20-shilling coins so called because they were first minted for British trade with Guinea (but soon in domestic use) and with gold from Africa. The original guinea (in use from 1663 to 1813) was based on the value of gold and by 1695 it was worth 30 shillings. William III then fixed its value at 21 shillings, 6 pence in 1698. The extra 6 pence were lopped off in December 1717.

The Guinea hen (1570s) is a domestic fowl imported from there. Guinea "derogatory term for Italian" (1896) was originally Guinea Negro (1740s) and meant "black person, person of mixed ancestry." It was applied to Italians c.1890 probably because of their dark complexions relative to northern Europeans, and after 1911 was occasionally applied to Hispanics and Pacific Islanders as well. New Guinea was so named 1546 by Spanish explorer Inigo Ortiz de Retes in reference to the natives' dark skin and tightly curled hair.
guinea pig
1660s, native to South America and perhaps so called either because it was first brought back to Britain aboard Guinea-men, ships that plied the triangle trade between England, Guinea, and South America [Barnhart, Klein]; or from confusion of Guinea (q.v.) with the South American region of Guyana (but OED is against this). In the extended sense of "one subjected to an experiment" it is first recorded 1920, because they were commonly used in vivisection experiments.
Guinevere
fem. proper name, from Welsh Gwenhwyvar, literally "white-cheeked."
Guinness
Irish brewery, founded 1759 by Arthur Guinness (1725-1803) in Dublin.
guise (n.)
late 13c., "style or fashion of attire," from Old French guise "manner, fashion, way," from Frankish *wisa or some similar Germanic source (cognate with Old High German wisa "manner, wise;" see wise (n.)). Sense of "assumed appearance" is from 1660s, from earlier meaning "mask, disguise" (c.1500).
guiser (n.)
"masquerader, mummer," late 15c., agent noun from guise.
guitar (n.)
1620s, ultimately from Greek kithara "cithara," a stringed musical instrument related to the lyre, perhaps from Persian sihtar (see sitar); the name reached English several times, including early 14c. giterne, from Old French, in reference to various stringed, guitar-like instruments; the modern word is directly from Spanish guittara (14c.), which ultimately is from the Greek. The Arabic word is perhaps from Spanish or Greek, though often the relationship is said to be the reverse.
guitarist (n.)
1770, from guitar + -ist.
gulag (n.)
system of prisons and labor camps, especially for political detainees, in the former Soviet Union; rough acronym from Russian Glavnoe upravlenie ispravitel'no-trudovykh lagerei "Chief Administration of Corrective Labor Camps," set up in 1931.
gulch (n.)
"deep ravine," 1832, American English, perhaps from obsolete or dialectal verb gulsh "sink in" (of land), "gush out" (of water), from Middle English gulchen "to gush forth; to drink greedily" (c.1200). Compare gulche-cuppe "a greedy drinker" (mid-13c.).
gules
"red," in heraldic descriptions, c.1300, from Old French goules "neckpiece of (red) fur," plural of gole, guele "throat," from Latin gula "throat" (see gullet).
gulf (n.)
late 14c., "profound depth;" geographic sense is c.1400; from Old French golf "a gulf, whirlpool," from Italian golfo "a gulf, a bay," from Late Latin colfos, from Greek kolpos "bay, gulf," earlier "trough between waves, fold of a garment," originally "bosom," the common notion being "curved shape," from PIE *kwelp- "to arch, to vault" (compare Old English hwealf, a-hwielfan "to overwhelm"). Latin sinus underwent the same development, being used first for "bosom," later for "gulf." Replaced Old English sæ-earm. Figurative sense of "a wide interval" is from 1550s. The Gulf Stream (1775) takes its name from the Gulf of Mexico.
gull (n.1)
shore bird, early 15c. (in a cook book), probably from Brythonic Celtic, compare Welsh gwylan "gull," Cornish guilan, Breton goelann; all from Old Celtic *voilenno-. Replaced Old English mæw (see mew (n.1)).
gull (n.2)
cant term for "dupe, sucker, credulous person," 1590s, of uncertain origin. Perhaps from verb meaning "to dupe, cheat" (1540s), earlier "to swallow" (1520s), ultimately from gull "throat, gullet" (early 15c.); see gullet. Or it is perhaps from (or influenced by) the bird (see gull (n.1)); in either case with a sense of "someone who will swallow anything thrown at him." Another possibility is Middle English dialectal gull "newly hatched bird" (late 14c.), which is perhaps from Old Norse golr "yellow," from the hue of its down.
Gullah
"of or pertaining to blacks on the sea-islands of Georgia and South Carolina," 1739 (first attested as a male slave's proper name), of uncertain origin. Early 19c. folk etymology made it a shortening of Angola (homeland of many slaves) or traced it to a W. African tribal group called the Golas.
gullet (n.)
c.1300 (as a surname), from Old French golet "neck (of a bottle); gutter; bay, creek," diminutive of gole "throat, neck" (Modern French guele), from Latin gula "throat," also "appetite," from PIE root *gwele- (3) "to swallow" (cognates: Latin gluttire "to gulp down, devour," Old English ceole "throat," Old Church Slavonic glutu "gullet," Old Irish gelim "I devour").
gullibility (n.)
1793, earlier cullibility (1728), probably from gull (n.2) "dupe, sucker" + -ability.