Online Etymology Dictionary

glare (v.): late 13c., "to shine brightly," from or related to Middle Dutch, Middle Low German glaren "to gleam," from Proto-Germanic *glaz-; the whole group represents a rhoticization of the root of glass (n.). Sense of "stare fiercely" is from late 14c. Related: Glared; glaring.
glare (n.): c. 1400, "bright light, dazzling glitter," from glare (v.); especially in reference to light reflected off some surface (17c.). From 1660s in sense of "fierce look." Old English glær (n.) meant "amber."
glaring (adj.): late 14c., "staring fiercely," present participle adjective from glare (v.). From 1510s of colors, etc., "vivid, dazzling;" meaning "obtrusively conspicuous" is from 1706. Related: Glaringly.
Glasgow: city in Scotland, from Gaelic, literally "green hollow," from glas "green, verdant" + cau "hollow."
glasnost (n.): 1972 (in reference to a letter of 1969 by Solzhenitsyn), from Russian glasnost "openness to public scrutiny," literally "publicity, fact of being public," ultimately from Old Church Slavonic glasu "voice," from PIE *gal-so-, from root *gal- (2) "to call, shout" (see call (v.)). First used in a socio-political sense by Lenin; popularized in English after Mikhail Gorbachev used it prominently in a speech of March 11, 1985, accepting the post of general secretary of the CPSU.
The Soviets, it seems, have rediscovered the value of Lenin's dictum that "glasnost," the Russian word for openness or publicity, is a desirable form of conduct. [New York Times news service article, March 1981]
glass (n.): Old English glæs "glass; a glass vessel," from Proto-Germanic *glasam "glass" (source also of Old Saxon glas, Middle Dutch and Dutch glas, German Glas, Old Norse gler "glass, looking glass," Danish glar), from PIE *ghel- (2) "to shine," with derivatives referring to bright materials and gold (source also of Latin glaber "smooth, bald," Old Church Slavonic gladuku, Lithuanian glodus "smooth"). The PIE root also is the ancestor of widespread words for gray, blue, green, and yellow, such as Old English glær "amber," Latin glaesum "amber" (which might be from Germanic), Old Irish glass "green, blue, gray," Welsh glas "blue."

Restricted sense of "drinking glass" is from early 13c. and now excludes other glass vessels. Meaning "a glass mirror" is from 14c. Meaning "glass filled with running sand to measure time" is from 1550s; meaning "observing instrument" is from 1610s.
glass (v.): late 14c., "to fit with glass;" 1570s, "to cover with glass," from glass (n.). Related: Glassed; glassing.
glass (adj.): Old English glæs, from glass (v.). Middle English also had an adjective glazen, from Old English glæsen. The glass snake (1736, actually a limbless lizard) is so called for the fragility of its tail. The glass slipper in "Cinderella" perhaps is an error by Charles Perrault, translating in 1697, mistaking Old French voir "ermine, fur" for verre "glass." In other versions of the tale it is a fur slipper. The proverb about people in glass houses throwing stones is attested by 1779, but earlier forms go back to 17c.:
Who hath glass-windows of his own must take heed how he throws stones at his house. ... He that hath a body made of glass must not throw stones at another. [John Ray, "Handbook of Proverbs," 1670]
Glass-house is from late 14c. as "glass factory," 1838 as "greenhouse."
glass-blower (n.): 1510s, from glass (n.) + blower. Related: Glass-blowing.
glasses (n.): "spectacles," 1660s, from plural of glass (n.).
glassful (n.): Old English glæsful "as much as a glass will hold;" see glass (n.) + -ful.
glassware (n.): 1745, from glass (adj.) + ware (n.).
glassy (adj.): late 14c., from glass (n.) + -y (2). From early 15c. in reference to the eye, etc., "fixed and expressionless."
Glastonbury: town in Somersetshire, famous as a prehistoric site, Old English Glestingabyrig, Glastingburi (725), "Stronghold (Old English byrig, dative of burh) of the people (Old English -inga-) living at Glaston," a Celtic name, possibly meaning "woad place."
glaucoma (n.): 1640s (cataracts and glaucoma not distinguished until c. 1705), from Latinized form of Greek glaukoma "cataract, opacity of the lens," perhaps from glaukommatos "gray-eyed," with omma "the eye" + glaukos, an adjective of uncertain origin (see glaucous).
glaucous (adj.): "dull bluish-green, gray," 1670s, from Latin glaucus "bright, sparkling, gleaming," also "bluish-green," of uncertain origin, from Greek glaukos, a word used in Homer of the sea as "gleaming, silvery" (apparently without a color connotation); used by later writers with a sense of "greenish" (of olive leaves) and "blue, gray" (of eyes). Homer's glauk-opis Athene probably originally was a "bright-eyed," not a "gray-eyed" goddess. Greek for "owl" was glaux from its bright, staring eyes. Middle English had glauk "bluish-green, gray" (early 15c.).
glaze (v.): late 14c. variant of Middle English glasen "to fit with glass," also "to make shine," from glas (see glass (n.)). The form probably influenced or reinforced by glazier. Of pottery, etc., "cover with a shiny or glossy substance," from c. 1400. Related: Glazed; glazing.
glaze (n.): "substance used to make a glossy coating," 1784, from glaze (v.). In reference to a thin coating of ice from 1752.
glazier (n.): "one who fits window glass into frames," early 15c. variant of late 14c. glasier (late 13c. as a surname, glasyer, from glass (v.) + -er (1). Influenced by French words in -ier. Alternative glazer recorded from c. 1400 as "one who applies coatings to earthenware."
gleam (n.): Old English glæm "a brilliant light; brightness; splendor, radiance, beauty," from Proto-Germanic *glaimiz (source also of Old Saxon glimo "brightness;" Middle High German glim "spark," gleime "glow-worm;" German glimmen "to glimmer, glow;" Old Norse glja "to shine, glitter, glisten"), from root *glim-, from PIE *ghel- (2) "to shine," with derivatives referring to bright materials and gold (see glass (n.), and compare glad (adj.)).
gleam (v.): early 13c., from gleam (n). Related: Gleamed; gleaming.
glean (v.): early 14c., "to gather by acquisition, scrape together," especially grains left in the field after harvesting, but the earliest use in English is figurative, from Old French glener "to glean" (14c., Modern French glaner) "to glean," from Late Latin glennare "make a collection," of unknown origin. Perhaps from Gaulish (compare Old Irish do-glinn "he collects, gathers," Celtic glan "clean, pure"). Figurative sense was earlier in English than the literal one of "gather grain left by the reapers" (late 14c.). Related: Gleaned; gleaning.
gleaner (n.): mid-15c., agent noun from glean (v.).
gleaning (n.): mid-14c., verbal noun from glean (n.). Related: Gleanings.
glebe (n.): late 14c., "soil of the earth; cultivated land;" also "a piece of land forming part of a clergyman's benefice," from Old French glebe, from Latin gleba, glaeba "clod, lump of earth," from PIE *glebh- "to roll into a ball" (source also of Latin globus "sphere;" Old English clyppan "to embrace;" Lithuanian glebys "armful," globti "to embrace, support").
glee (n.): Old English gliu, gliw, gleow "entertainment, mirth (usually implying music); jest, play, sport," also "music" and "mockery," presumably from a Proto-Germanic *gleujam but absent in other Germanic languages except for the rare Old Norse gly "joy;" probably related to the group of Germanic words in gl- with senses of "shining; smooth; radiant; joyful" (see glad). A poetry word in Old English and Middle English, obsolete c. 1500-c. 1700, it somehow found its way back to currency late 18c. In Old English, an entertainer was a gleoman (female gleo-mægden).

Glee club (1814) is from the secondary sense of "musical composition for three or more solo voices, unaccompanied, in contrasting movement" (1650s), a form of musical entertainment that flourished 1760-1830.
gleeful (adj.): 1580s, from glee + -ful. Related: Gleefully. Alternative gleesome attested from c. 1600.
gleek (n.): old three-person card game, 1530s, from French glic, ghelicque (15c.), perhaps from Middle Dutch ghelic (Dutch gelijk) "like, alike" because one of the goals of the game is collecting three cards of the same rank.
gleen (n.): "gleam of sunlight," 1650s, probably from a Scandinavian dialectal word; compare Swedish dialectal glena, Danish dialectal glene "clear patch of sky."
gleet (n.): mid-14c., "slime, greasy filth," from Old French glete "clay, loam; slime, mud, filth" (12c., Modern French glette), from Latin glitem (nominative glis) "sticky, glutinous ground," back-formation from glittus "sticky."
glen (n.): "narrow valley," late 15c., from Scottish, from Gaelic gleann "mountain valley" (cognate with Old Irish glenn, Welsh glyn). Common in place names such as Glenlivet (1822), a kind of whiskey, named for the place it was first made (literally "the glen of the Livet," a tributary of the Avon); and Glengarry (1841) a kind of men's cap, of Highland origin, named for a valley in Inverness-shire.
glib (adj.): 1590s, "smooth and slippery," a dialect word, possibly a shortening of obsolete glibbery "slippery," which is perhaps from Low German glibberig "smooth, slippery," from Middle Low German glibberich, from or related to glibber "jelly," all part of the Germanic group of gl- words for "smooth, shining, joyful" (see glad (adj.)). Of words, speakers, etc., from c. 1600. Related: Glibly; glibness.
glide (v.): Old English glidan "move along smoothly and easily; glide away, vanish; slip, slide" (class I strong verb, past tense glad, past participle gliden), from Proto-Germanic *glidon "to glide" (source also of Old Saxon glidan, Old Frisian glida, Old High German glitan, German gleiten), probably part of the large group of Germanic words in gl- involving notions of "smooth; shining; joyful" (see glad (adj.)). Related: Glided; gliding. Strong past tense form glid persisted into 20c.
glide (n.): 1580s, from glide (v.). From 1835 as a term in music; from 1889 as a step in dancing or a type of dance.
glider (n.): mid-15c., "person or thing that glides," agent noun from glide. Meaning "motorless airplane" is c. 1897.
glim (n.): in 18c. slang, "a light, candle, lantern" (1700); in 19c. slang "an eye" (1820), probably a back-formation from glimmer (n.) or in some cases glimpse (n.). Related: Glims.
glimmer (v.): late 14c., "to shine brightly;" early 15c., "to shine dimly," perhaps from or related to Middle Dutch glimmen, Middle Low German glimmern, from an extended (frequentative?) form of Proto-Germanic *glim-, root of Old English glæm "brightness" (see gleam (n.)). Sense shifted 15c. to "shine faintly." Compare Dutch glimmeren, German glimmeren "to shine dimly." Related: Glimmered; glimmering.
glimmer (n.): 1580s, "a faint, wavering light," from glimmer (v.).
glimpse (v.): c. 1400, "to glisten, be dazzling," probably from Old English *glimsian "shine faintly," part of the group of Germanic words in *gl- having to do with "smooth; shining; joyous" (see gleam (n.)). If so, the intrusive -p- would be there to ease pronunciation. From mid-15c. as "to glance with the eyes;" from 1779 as "catch a quick view." Related: Glimpsed; glimpsing.
glimpse (n.): 1530s, "faint or transient appearance," from glimpse (v.). From 1570s as "a brief and imperfect view." Earlier was the verbal noun glimpsing "imperfect vision" (late 14c.).
glint (v.): 1787 (intransitive), from Scottish, where apparently it survived as an alteration of glent, from Middle English glenten "gleam, flash, glisten" (mid-15c.), from a Scandinavian source (compare Norwegian gletta "to look," dialectal Swedish glinta "to shine"), from the group of Germanic *gl- words meaning "smooth; shining; joyous," from PIE *ghel- (2) "to shine," with derivatives referring to bright materials and gold (see glass (n.)). Reintroduced into literary English by Burns. Related: Glinted; glinting.
glint (n.): "a gleam," 1826 (with a possible isolated use from 1540s in OED), from glint (v.).
glioma (n.): type of brain tumor, 1870, medical Latin, literally "glue tumor," from Greek glia "glue" (from PIE *glei- "to stick together;" see clay) + -oma. Related: Gliomatosis; gliomatous.
glissade (n.): in dancing, 1843, from French glissade, from glisser "to slip, slide" (13c.), from Frankish *glidan or some other Germanic source (cognate with Dutch glissen), from Proto-Germanic *glidan "to glide" (see glide (v.)). Earlier in English as a verb (1832).
glissando: in music, "glidingly, flowingly" (1842), also, as a noun, "a gliding from one note to the next," an Italianized form of French glissant, present participle of glisser "to slide" (see glissade). Related: Glissato; glissicando; glissicato.
glisten (v.): Old English glisnian "to glisten, gleam," from Proto-Germanic *glis- (source also of Old English glisian "to glitter, shine," Old Frisian glisa "to shine," Middle High German glistern "to sparkle," Old Danish glisse "to shine"), from PIE *ghleis-, from root *ghel- (2) "to shine," with derivatives referring to bright materials and gold (see glass (n.), and compare glint and glad). Related: Glistened; glistening.
glistening (adj.): late 14c., present participle adjective from glisten (v.).
glister (v.): late 14c., "to glitter, sparkle," probably from or related to Low German glisteren, Middle Dutch glisteren, frequentative forms ultimately from the large group of Germanic gl- words for "smooth; shining; joyful," from PIE root *ghel- (2) "to shine, glitter" (see glass (n.)). Related: Glistered; glistering. As a noun, from 1530s.
All is not golde that glistereth [Thomas Becon, "Reliques of Rome," 1563]
glitch (n.): 1959, American English, possibly from Yiddish glitsh "a slip," from glitshn "to slip," from German glitschen, and related gleiten "to glide" (see glide (v.)). Perhaps directly from German. Apparently it began as technical jargon among radio and television engineers, but was popularized and given a broader meaning c. 1962 by the U.S. space program.
All you get today is "glitch" wherever splicing occurs. "Glitch" is slang for the "momentary jiggle" that occurs at the editing point if the sync pulses don't match exactly in the splice. [Sponsor, Volume 13, June 20, 1959]
glitter (v.): c. 1300, glideren (late 14c. as gliteren), from an unrecorded Old English word or from a Scandinavian source such as Old Norse glitra "to glitter," from Proto-Germanic *glit- "shining, bright" (source also of Old English glitenian "to glitter, shine; be distinguished," Old High German glizzan, German glitzern, Gothic glitmunjan), from PIE *ghleid- (source also of Greek khlidon, khlidos "ornament"), from root *ghel- (2) "to shine," with derivatives referring to bright materials and gold (see glass (n.)). Related: Glittered; glittering. Other Middle English words for "to glitter" include glasteren and glateren.