Online Etymology Dictionary

Druid (n.): 1560s, from French druide, from Latin druidae (plural), from Gaulish Druides, from Celtic compound *dru-wid-, probably representing Old Celtic *derwos "true"/PIE *dru- "tree" (especially oak; see tree (n.)) + *wid- "to know" (see vision). Hence, literally, perhaps, "they who know the oak" (perhaps in allusion to divination from mistletoe). Anglo-Saxon, too, used identical words to mean "tree" and "truth" (treow).

The English form comes via Latin, not immediately from Celtic. The Old Irish form was drui (dative and accusative druid; plural druad); Modern Irish and Gaelic draoi, genitive druadh "magician, sorcerer." Not to be confused with United Ancient Order of Druids, secret benefit society founded in London 1781.
Druidess (n.): 1755, from Druid + -ess. Formerly, Druid had been used indifferently of both sexes.
Druidic (adj.): 1773, from Druid + -ic. Related: Druidical.
drum (n.): 1540s, probably from Middle Dutch tromme "drum," common Germanic (compare German Trommel, Danish tromme, Swedish trumma), probably of imitative origin. Not common before 1570s. Slightly older, and more common at first, was drumslade, apparently from Dutch or Low German trommelslag. Machinery sense attested from 1740, from similarity of shape.
drum (v.): 1570s, from drum (n.). To drum (up) business, etc., is American English 1839, from the old way of drawing a crowd.
drumlin (n.): 1833, diminutive of drum (1725) "ridge or long, narrow hill," often separating two parallel valleys, from Gaelic and Irish druim "back, ridge."
drummer (n.): 1570s, agent noun from drum (v.).
Drummond light (n.): "calcium light, torch that burns calcium oxide (lime) and gives off intense white light," 1854, named for Scottish engineer Capt. Thomas Drummond, R.E., (1797-1840), who invented it c. 1825.
drumstick (n.): 1580s, from drum (n.) + stick (n.); applied to the lower joint of cooked fowl 1764.
drunk (adj.): past participle of drink, used as an adjective from mid-14c. in sense "intoxicated." In various expressions, such as "drunk as a lord" (1891); Chaucer has "dronke ... as a Mous" (c. 1386); and, from 1709, "as Drunk as a Wheelbarrow." Medieval folklore distinguished four successive stages of drunkenness, based on the animals they made men resemble: sheep, lion, ape, sow. Drunk driver first recorded 1948. Drunk-tank "jail cell for drunkards" attested by 1912, American English. The noun meaning "drunken person" is from 1852; earlier this would have been a drunkard.
drunkard (n.): 1520s, droncarde, but probably older (attested from late 13c. as a surname, Druncard), from Middle English dronken, participial adjective from drunk (q.v.), + -ard.
drunken (adj.): full form of the past participle of drunk. Meaning "inebriated" was in Old English druncena; adjectival meaning "habitually intoxicated" is from 1540s. Related: Drunkenly.
drunkenness (n.): Old English druncennysse; see drunken + -ness.
drupe (n.): 1753, from Modern Latin drupa "stone-fruit," from Latin drupa (oliva) "wrinkled olive," from Greek dryppa, short for drypepes "tree-ripened," from drys "tree" + pepon "ripe" (see pumpkin).
Druse: member of a Muslim sect centered in Lebanon, 1786, from Arabic duruz, plural of darazi, from name of the sect founder, Ismail ad-Darazi (11c.), literally "Ismail the Tailor."
Drusilla: fem. proper name, Latin fem. diminutive of Drusus, frequent surname in Livian gens, earlier Drausus, perhaps a Celtic word meaning literally "strong" (compare Old Celtic *dru- "oak," also "strong;" see Druid).
druthers (n.): 1895, from jocular formation based on I'd ruther, American English dialectal form of I'd rather (used by Bret Harte as drathers, 1875).
dry (adj.): Old English dryge, from Proto-Germanic *draugiz (source also of Middle Low German dröge, Middle Dutch druge, Dutch droog, Old High German trucchon, German trocken, Old Norse draugr), from Germanic root *dreug- "dry."

Meaning "barren" is mid-14c. Of humor or jests, early 15c. (implied in dryly); as "uninteresting, tedious" from 1620s. Of places prohibiting alcoholic drink, 1870 (but dry feast, one at which no liquor is served, is from late 15c.; colloquial dry (n.) "prohibitionist" is 1888, American English). Dry goods (1708) were those measured out in dry, not liquid, measure. Dry land (that not under the sea) is from early 13c. Dry run is from 1940s.
dry (v.): Old English drygan, related to dry (adj.). Related: Dried; drying. Of the two agent noun spellings, drier is the older (1520s), while dryer (1874) was first used of machines. Dry out in the drug addiction sense is from 1967. Dry up "stop talking" is 1853.
dryad (n.): 1550s, from Latin dryas, from Greek dryas (plural dryades) "wood nymph," from drus (genitive dryos) "oak," from PIE *deru- "tree, wood, oak" (see tree (n.)).
dryer (n.): agent noun from dry (v.).
du jour (adj.): from French plat du jour "dish of the day," early 20c. on restaurant menus, abstracted as an all-purpose modifier 1989.
dual (adj.): c. 1600, from Latin dualis, from duo "two" (see two). Related: Dually.
dualism (n.): 1755 as a term in philosophy, from French dualisme (1754); also used in theological senses; see dual + -ism.
dualistic (adj.): 1801, from stem of dualism + -istic.
duality (n.): late 14c., from Old French dualité (14c.), from Late Latin dualitas, from Latin dualis (see dual).
dub (v.1): "give a name to," originally "make a knight," from late Old English dubbian "knight by striking with a sword" (11c.), a late word, perhaps borrowed from Old French aduber "equip with arms, adorn" (11c.) which is of uncertain origin, but there are phonetic difficulties. Meaning "provided with a name" is from 1590s. Related: Dubbed; dubbing.
dub (v.2): "add or alter sound on film," 1929, shortening of double; so called because it involves re-recording voices onto a soundtrack. The type of re-mixed reggae music was so called from 1974, probably for the same reason. Related: Dubbed; dubbing.
Dubai: Gulf coast emirate, of uncertain origin.
dubiety (n.): c. 1750, from Late Latin dubietas "doubt, uncertainty," from Latin dubius "vacillating, fluctuating," figuratively "wavering in opinion, doubting" (see dubious).
dubious (adj.): 1540s, from Latin dubiosus "doubtful," from dubium "doubt," neuter of dubius "vacillating, moving two ways, fluctuating;" figuratively "wavering in opinion, doubting, doubtful," from duo "two" (see two), with a sense of "of two minds, undecided between two things." Old English also used tweo "two" to mean "doubt." Compare doubt (v.). Related: Dubiously; dubiousness.
dubitation (n.): mid-15c., from Middle French dubitation (13c.), from Latin dubitationem (nominative dubitatio) "uncertainty, doubt," noun of state from past participle stem of dubitare "to waver in opinion, be uncertain, doubt, question" (related to dubius "uncertain;" see dubious).
Dublin: capital of Ireland, literally "black pool," from Irish dubh "black" + linn "pool." In reference to the dark waters of the River Liffey.
Dubonnet (n.): sweet French aperitif, 1913, trademark name, from the name of a family of French wine merchants.
ducal (adj.): late 15c., from Middle French ducal (15c.), from Late Latin ducalis, from Latin dux (genitive ducis); see duke (n.).
ducat (n.): late 14c., from Old French ducat (late 14c.), from Italian ducato (12c.), from Medieval Latin ducatus "coin," originally "duchy," from dux (genitive ducis) "duke" (see duke (n.)).

So called for the name or effigy of Roger II of Sicily, Duke of Apulia, which first issued the coins (c.1140). Byzantine emperor Constantine X had the Greek form doux struck on his coins during his reign (1059-1067). Over the years it was a unit of currency of varying value in Holland, Russia, Austria, Sweden, Venice, etc. Remained popular in slang for "money" or "ticket" from its prominence in "The Merchant of Venice."
Duce (n.): 1923, title assumed by Benito Mussolini (1883-1945); Italian, literally "leader," from Latin ducem (see duke (n.)).
duchess (n.): c. 1300, from Old French duchesse, from Late Latin or Medieval Latin ducissa, fem. of dux (see duke (n.)). Often spelled dutchess until early 19c. (as in Dutchess County, New York, U.S.).
duchy (n.): mid-14c., "territory ruled by a duke or duchess," from Old French duché (12c.), from Medieval Latin ducatus, from Latin dux (see duke (n.)).
duck (n.1): waterfowl, Old English duce (found only in genitive ducan) "a duck," literally "a ducker," presumed to be from Old English *ducan "to duck, dive" (see duck (v.)). Replaced Old English ened as the name for the bird, this being from PIE *aneti-, the root of the "duck" noun in most Indo-European languages.
In the domestic state the females greatly exceed in number, hence duck serves at once as the name of the female and of the race, drake being a specific term of sex. [OED]
As a term of endearment, attested from 1580s. duck-walk is 1930s; duck soup "anything easily done" is by 1899. Duck's ass haircut is from 1951. Ducks-and-drakes, skipping flat stones on water, is from 1580s; the figurative sense of "throwing something away recklessly" is c. 1600.
duck (n.2): "strong, untwilled linen (later cotton) fabric," used for sails and sailors' clothing, 1630s, from Dutch doeck "linen cloth" (Middle Dutch doec), related to German Tuch "piece of cloth," Danish dug, Old Frisian dok, Old High German tuoh, all of unknown origin.
duck (v.): "to plunge into" (transitive), c. 1300; to suddenly go under water (intransitive), mid-14c., from presumed Old English *ducan "to duck," found only in derivative duce (n.) "duck" (but there are cognate words in other Germanic languages, such as Old High German tuhhan "to dip," German tauchen "to dive," Old Frisian duka, Middle Dutch duken "to dip, dive," Dutch duiken), from Proto-Germanic *dukjan.

Sense of "bend, stoop quickly" is first recorded in English 1520s. Related: Ducked; ducking. The noun is attested from 1550s in the sense of "quick stoop;" meaning "a plunge, dip" is from 1843.
duckling (n.): mid-15c., dookelynge, from duck (n.) + -ling. The ugly duckling is from Hans Christian Andersen's tale (1843 in Danish, by 1846 in English).
ducky (adj.): "excellent," slang from 1897 (often ironical),perhaps from duckie as a term of endearment (early 19c.). Probably not related to much earlier slang noun meaning "a woman's breast" ["...whose pritty duckys I trust shortly to kysse," Henry VIII, c. 1536 letter to Anne Boleyn, who, contrary to rumor, did not have three of them].
duct (n.): 1640s, "course, direction," from Latin ductus "a leading," past participle of ducere "to lead" (see duke (n.)). Anatomical sense is from 1660s. Meaning "conduit, channel" is 1713; that of "air tube in a structure" is from 1884.
duct tape: by 1943; see duct (here in the electrical wiring sense) + tape.
ductile (adj.): mid-14c., from Old French ductile or directly from Latin ductilis "that may be led or drawn," from past participle of ducere "to lead" (see duke (n.)). Related: Ductility.
dud (n.): c. 1825, "person in ragged clothing," from duds (q.v.). Sense extended by 1897 to "counterfeit thing," and 1908 to "useless, inefficient person or thing." This led naturally in World War I to "shell which fails to explode," and thence to "expensive failure."
dude (n.): 1883, "fastidious man," New York City slang of unknown origin; recent research suggests it is a shortening of Yankee Doodle, based on the song's notion of "foppish, over-fastidious male" (compare macaroni). The vogue word of 1883, originally used in reference to the devotees of the "aesthetic" craze, later applied to city slickers, especially Easterners vacationing in the West (as in dude ranch, first recorded 1921).
Now, "tenderfoot" is not to be construed as the Western equivalent of that much evolved and more abused specimen of mankind, familiarly styled "dude." For even the Montana cowboy recognizes the latter. Not that he has ever seen the true prototype of a class that was erstwhile so numerous among us. But he is convinced that a person caught in the act of wearing a white linen collar, and who looks as though he might have recently shaved or washed his face, must be a dude, true and proper. ["Random Notes and Observations of a Trip through the Great Northwest," "The Medical Record," Oct. 20, 1883]
Application to any male is recorded by 1966, U.S., originally in African-American vernacular.
dudette (n.): by 1991, from dude in the surfer/teen slang sense + fem. ending -ette. Earlier (in the Old West sense) were dudine (1883), dudess (1885).