Online Etymology Dictionary

gravitas (n.): 1924, from Latin gravitas "weight, heaviness;" figuratively, of persons, "dignity, presence, influence" (see gravity). A word that became useful when gravity acquired a primarily scientific meaning.
gravitate (v.): 1640s, "exert weight, move downward," from Modern Latin gravitatus, past participle of gravitare "gravitate," from Latin gravitas "heaviness, weight" (see gravity). Meaning "To be affected by gravity" is from 1690s. Figurative use from 1670s. Related: Gravitated; gravitating. The classical Latin verb was gravare "to make heavy, burden, oppress, aggravate."
gravitation (n.): 1640s in physics sense, also figurative, from Modern Latin gravitationem (nominative gravitatio), noun of action from past participle stem of gravitare (see gravitate). Related: Gravitational.
gravity (n.): c.1500, "weight, dignity, seriousness," from Middle French gravité "seriousness, thoughtfulness," and directly from Latin gravitatem (nominative gravitas) "weight, heaviness, pressure," from gravis "heavy" (see grave (adj.)). The scientific sense of "force that gives weight to objects" first recorded 1640s.
gravure: 1893, short for photogravure, from gravure, from grave (v.) + -ure.
gravy (n.): late 14c. (early 14c. in Anglo-French), from Old French grané (with -n- misread for -u- -- the character used for -v- in medial positions in words in medieval manuscripts) "sauce, stew," probably originally "properly grained, seasoned," from Latin granum "grain, seed" (see corn (n.1)). See discussion in OED. Meaning "money easily acquired" first attested 1910; gravy train (1927) was originally railroad slang for a short haul that paid well.
gray (adj.): Old English græg (Mercian grei), from Proto-Germanic *grisja- "gray" (cf. Old Norse grar, Old Frisian gre, Middle Dutch gra, Dutch graw, Old High German grao, German grau), with no certain cognates outside Germanic. French gris, Spanish gris, Italian grigio, Medieval Latin griseus are Germanic loan-words.

The distinction between British grey and U.S. gray developed 20c. The noun is c.1200, from the adjective. Gray as figurative for "Southern troops in the U.S. Civil War" is first recorded 1863, in reference to their uniform color. Expression the gray mare is the better horse in reference to households ruled by wives is recorded from 1540s. The verb is 1610s (with an isolated instance from late 14c.). Related: Grayed; graying.
grayling (n.): trout-like freshwater fish, early 14c., from gray + diminutive suffix -ling.
graze (v.1): "to feed," Old English grasian "to feed on grass," from græs "grass" (see grass). Cf. Middle Dutch, Middle High German grasen, Dutch grazen, German grasen. Figurative use by 1570s. Related: Grazed; grazing.
graze (v.2): "to touch," c.1600, perhaps a transferred sense from graze (1) via a notion of cropping grass right down to the ground (cf. German grasen "to feed on grass," used in military sense in reference to cannonballs that rebound off the ground). Related: Grazed; grazing. As a noun from 1690s.
grazier (n.): late 13c. as a surname, agent noun from graze (v.1).
grease (n.): c.1300, from Anglo-French grece, from Old French gresse, craisse "grease, fat" (Modern French graisse), from Vulgar Latin *crassia "(melted) animal fat, grease," from Latin crassus "thick, solid, fat" (cf. Spanish grasa, Italian grassa). Grease paint, used by actors, attested from 1888. Grease monkey "mechanic" is from 1928.
grease (v.): c.1300, from grease (n.). Sense of "ply with bribe or protection money" is 1520s, from notion of grease the wheels "make things run smoothly" (mid-15c.). To grease (someone's) palm is from 1580s. Expression greased lightning, representing something that goes very fast, is American English, by 1832.
greaser (n.): early 14c. (as a surname), "one who smears salve on a sheep," agent noun from from grease. As derogatory American English slang for "native Mexican or Latin American," first attested 1849, so called from appearance. Greaseball in same sense from 1934.
greasy (adj.): 1510s, from grease + -y (2). Related: Greasily; greasiness. Greasy spoon "small cheap restaurant" is from 1925.
great (adj.): Old English great "big, tall, thick, stout; coarse," from West Germanic *grautaz "coarse, thick" (cf. Old Saxon grot, Old Frisian grat, Dutch groot, German groß "great").

Said to have meant originally "big in size, coarse," and, if so, perhaps from PIE root *ghreu- "to rub, grind." It took over much of the sense of Middle English mickle, and is now largely superseded by big and large except for non-material things.

As a prefix to terms denoting "kinship one degree further removed" (early 15c., earliest attested use is in great uncle) it is from the similar use of French grand, itself used as the equivalent of Latin magnus. An Old English way of saying "great-grandfather" was þridda fæder, literally "third father."

In the sense of "excellent, wonderful" great is attested from 1848. Great White Way "Broadway in New York City" is from 1901. Great Spirit "high deity of the North American Indians," 1703, originally translates Ojibwa kitchi manitou. The Great War originally (1887) referred to the Napoleonic Wars, later (1914) to what we now call World War I (see world).
"The Great War" -- as, until the fall of France, the British continued to call the First World War in order to avoid admitting to themselves that they were now again engaged in a war of the same magnitude. [Arnold Toynbee, "Experiences," 1969]
Also formerly with a verb form, Old English greatian, Middle English greaten "to become larger, increase, grow; become visibly pregnant," which became archaic after 17c.
Great Britain: c.1400, Grete Britaigne. As opposed to Brittany.
great-grandfather (n.): 1510s, from great + grandfather.
great-grandmother (n.): 1520s, from great + grandmother.
great-hearted (adj.): late 14c., from great + hearted.
greatcoat (n.): "large, heavy overcoat," 1660s, from great + coat (n.).
greater: Old English gryttra, Anglian *gretra; comparative of great.
greatest (adj.): early 13c., superlative of great.
greatly (adv.): c.1200, from great + -ly (2). Cf. Middle Dutch grotelike, Dutch grootelijks.
greatness (n.): late Old English gretnys "thickness, coarseness, stoutness;" see great + -ness. Meaning "eminence" is early 14c.
greave (n.): leg armor, c.1300, from Old French greve "shin, armor for the leg" (12c.), of unknown origin. [Klein suggests it ultimately is from Egyptian Arabic gaurab "stocking, apparel for the leg."]
greaves (n.): mid-14c., plural of greave.
grebe (n.): diving bird, 1766, from French grèbe, of unknown origin, possibly from Breton krib "a comb," since some species are crested.
Grecian (adj.): c.1400, from Latin Graecia “Greece” (see Greek) + people ending -ian. The noun meaning "a Greek" is from early 15c.
Greco-: see Graeco-.
Greece: c.1300, from Latin Graecia; named for its inhabitants; see Greek. Earlier in English was Greklond (c.1200). The Turkish name for the country, via Persian, is Yunanistan, literally "Land of the Ionians." Ionia also yielded the name for the country in Arabic and Hindi (Yunan).
greed (n.): c.1600, a back-formation from greedy.
greedily (adv.): Old English grædiglice; see greedy + -ly (2).
greediness (n.): Old English grædignes; see greedy + -ness.
greedy (adj.): Old English grædig (West Saxon), gredig (Anglian) "voracious," also "covetous," from Proto-Germanic *grædagaz (cf. Old Saxon gradag "greedy," Old Norse graðr "greed, hunger," Danish graadig, Dutch gretig, Old High German gratag "greedy"), from *græduz (cf. Gothic gredus "hunger," Old English grædum "eagerly"), possibly from PIE root *gher- "to like, want" (cf. Sanskrit grdh "to be greedy").

In Greek, the word was philargyros, literally "money-loving." A German word for it is habsüchtig, from haben "to have" + sucht "sickness, disease," with sense tending toward "passion for."
Greek (n.): Old English Grecas, Crecas (plural), early Germanic borrowing from Latin Graeci "the Hellenes," from Greek Grakoi. Aristotle, who was the first to use Graikhos as equivalent to Hellenes ("Meteorologica" I.xiv), wrote that it was the name originally used by Illyrians for the Dorians in Epirus, from Graii, native name of the people of Epirus.

But a modern theory (put forth by German classical historian Georg Busolt, 1850-1920), derives it from Graikhos "inhabitant of Graia" (literally "gray"), a town on the coast of Boeotia, which was the name given by the Romans to all Greeks, originally to the Greek colonists from Graia who helped found Cumae (9c. B.C.E.), the important city in southern Italy where the Latins first encountered Greeks. Under this theory, it was reborrowed in this general sense by the Greeks.

The Germanic languages originally borrowed the word with an initial -k- sound (cf. Old High German Chrech, Gothic Kreks), which probably was their initial sound closest to the Latin -g- at the time; the word was later refashioned.
It was subtle of God to learn Greek when he wished to become an author -- and not to learn it better. [Nietzsche, "Beyond Good and Evil," 1886]
Meaning "the Greek language" is from late 14c.; meaning "unintelligible speech, gibberish" is from c.1600. Meaning "Greek letter fraternity member" is student slang, 1900.
Greek (adj.): late 14c., from Greek (n.). Earlier Gregeis (c.1300), from Old French Gregois; also Greekish (Old English Grecisc). In venery, "anal," by 1970. Greek gift is from "Æneid," II.49: "timeo Danaos et dona ferentes."
green (n., adj.): Old English grene "green, young, immature, raw," earlier groeni, from West Germanic *gronja- (cf. Old Saxon grani, Old Frisian grene, Old Norse grænn, Danish grøn, Dutch groen, Old High German gruoni, German grün), from PIE root *ghre- "grow" (see grass), through sense of "color of living plants."

Meaning "a field, grassy place" was in Old English. Sense of "of tender age, youthful" is from early 15c.; hence "gullible" (c.1600). The color of jealousy at least since Shakespeare (1596); "Greensleeves," ballad of an inconstant lady-love, is from 1570s. Green light in figurative sense of "permission" is from 1937. Green and red as signals on railways first attested 1883, as nighttime substitutes for semaphore flags. Green beret originally "British commando" is from 1949. Green room "room for actors when not on stage" is from 1701; presumably a well-known one was painted green.
green (v.): Old English grenian (see green (n.,adj.)). Related: Greened; greening.
greenback (n.): "U.S. dollar bill," 1862, so called from the time of their introduction, from green (adj.) + back (n.); bank paper money printed in green ink had been called this since 1778 (as opposed to redbacks, etc.).
greenery (n.): 1797, from green + -ery.
greengage: from green + name of English botanist Sir William Gage (1657-1727) who first cultivated it in England c.1725.
greengrocer (n.): 1723, from green "vegetables" + grocer.
greenhead (n.): 1580s, "young, untrained intellect," from green (adj.) + head (n.). As a type of biting fly, by 1837.
greenhorn (n.): mid-15c., "young horned animal," from green (adj.) in sense of "new, fresh, recent" + horn (n.). Applied to new soldiers from c.1650; extended to any inexperienced person by 1680s.
greenhouse (n.): 1660s, from green + house (n.). Greenhouse effect attested from 1937.
greenish (adj.): late 14c., from green + -ish.
Greenland: Old Norse Groenland, so named by its discoverer (986 C.E.) because "it would induce settlers to go there, if the land had a good name":
Hann gaf nafn landinu ok kallaði Groenland, ok kvað menn þat myndu fysa þangat farar, at landit ætti nafn gott. [Islendingabok, 1122-1133]
greenness (n.): Old English grennes; see green + -ness. Meaning "immaturity" is from early 15c. Walpole coined greenth (1753) in the same sense.
greens (n.): "freshly cut branches used for decoration," 1690s; "vegetables," 1725, from green. Greens "ecology political party," first recorded 1978, from German die Grünen (West Germany), an outgrowth of Grüne Aktion Zukunft "Green Campaign for the Future," a mainly anti-nuclear power movement, and/or grüne Listen "green lists" (of environmental candidates). Green (adj.) in the sense of "environmental" is attested from 1972; Greenpeace, the international conservation and environmental protection group, is from 1971.