Online Etymology Dictionary

rosewood (n.): 1650s, from rose (n.1) + wood (n.). The name is due to the scent of some species when freshly cut.
Rosh Hashanah (n.): Jewish new year, 1846, from Hebrew rosh hashshanah, literally "head of the year," from rosh "head of" + hash-shanah "the year."
Rosicrucian (n.): 1620s, from Modern Latin rosa crucis (DuCange) or crux, Latinization of German Rosenkreuz, French rosecroix, from the secret society's reputed founder Christian Rosenkreuz, said to date from 1484, but not mentioned before 1614. As an adjective from 1660s.
rosin (n.): late 13c., from Old French raisine, rousine, variants of résine (see resin). The verb is from mid- 14c. Related: Rosined; rosining.
Rosinante (n.): Don Quixote's horse, from Spanish Rocinante, from rocin "worn-out horse" + antes "before," "so called in allusion to the circumstance that Don Quixote's charger was formerly a wretched hack" [Klein]. Rocin is cognate with Old French rancin "draft horse, hack," but the word is of unknown origin.
roster (n.): 1727, from Dutch rooster "table, list," originally "gridiron," from Middle Dutch roosten "to roast" (see roast (v.)). So called from the grid of lines drawn on a paper to make a list.
rostral (adj.): c. 1400, from Late Latin rostralis, from Latin rostrum "beak" (see rostrum).
rostrum (n.): 1540s, from Latin rostrum, name of the platform stand for public speakers in the Forum in ancient Rome. It was decorated with the beaks of ships taken in the first naval victory of the Roman republic, over Antium, in 338 B.C.E., and the word's older sense is "end of a ship's prow," literally "beak, muzzle, snout," originally "means of gnawing," instrument noun form of rodere "to gnaw" (see rodent). Compare claustrum "lock, bar," from claudere "to shut." Extended sense of any platform for public speaking is first recorded 1766. Classical plural form is rostra.
rosy (adj.): late 14c., of a color, from rose (n.1) + -y (2), probably modeled on Old French rose. From 1590s of healthy complexions; 1775 in the sense "cheerful;" meaning "promising" is from 1887. Similar formation in Middle Dutch rosich, Dutch rozig, German rosig.
rot (v.): Old English rotian "to decay, putrefy," from Proto-Germanic *rutjan (source also of Old Saxon roton, Old Norse rotna, Old Frisian rotia, Middle Dutch roten, Dutch rotten, Old High German rozzen "to rot," German rößen "to steep flax"), from stem *rut-. Related: Rotted; rotting.
rot (n.): early 14c., from rot (v.) or of Scandinavian origin (compare Icelandic rot, Swedish röta, Danish røde "decay, putrefaction"), from the root of the verb. Slang noun sense of "rubbish, trash" is from 1848.
rotary (adj.): 1731, from Medieval Latin rotarius "pertaining to wheels," from Latin rota "a wheel, a potter's wheel; wheel for torture," from PIE root *ret- "to run, to turn, to roll" (source also of Sanskrit rathah "car, chariot;" Avestan ratho; Lithuanian ratas "wheel," ritu "I roll;" Old High German rad, German Rad, Dutch rad, Old Frisian reth, Old Saxon rath, Old Irish roth, Welsh rhod "carriage wheel"). The international service club (founded by Paul P. Harris in Chicago in 1905) so called from the practice of clubs entertaining in rotation. Hence Rotarian (1911).
rotate (v.): 1794, intransitive, back-formation from rotation. Transitive sense from 1823. Related: Rotated; rotating. Rotator "muscle which allows a part to be moved circularly" is recorded from 1670s.
rotation (n.): 1550s, from Latin rotationem (nominative rotatio) "a turning about in a circle," noun of action from past participle stem of rotare "turn round, revolve, whirl about, roll," from PIE *ret- "to run, roll" (see rotary).
rotational (adj.): 1852, from rotation + -al (1).
rotavirus (n.): wheel-shaped virus causing inflammation of the lining of the intestines, 1974, from Latin rota "wheel" (see rotary) + virus.
rote (n.): c. 1300, "custom, habit," in phrase bi rote "by heart," of uncertain origin, sometimes said to be connected with Old French rote "route" (see route (n.)), or from Latin rota "wheel" (see rotary), but OED calls both suggestions groundless.
rotgut (n.): also rot-gut, "unwholesome liquor," 1630s, from rot (v.) + gut (n.).
Rothschild: "rich person," 1833, in reference to the international banking family descended from Mayer Amschel Rothschild (1744-1812) of Frankfurt. The surname is literally "red shield," a house name.
Rotifera (n.): class of microscopic freshwater organisms, 1830, Modern Latin, from Rotifer (Leeuwenhoek, 1702), from Latin rota "wheel" (see rotary) + -fer "bearing" (see bear (v.)). The animalcules use rotary organs to swim about.
rotisserie (n.): 1868, "restaurant where meat is roasted on a spit," from French rôtisserie "shop selling cooked food, restaurant," from present participle stem of rôtir "to roast," from Old French rostir (see roast (v.)). As an in-home cooking apparatus, attested from 1953. Manufacturers (or their copy writers) back-formed a verb, rotiss (1958). Rotisserie league (1980), a form of fantasy baseball, is based on La Rotisserie, the Manhattan restaurant where it was conceived.
rotogravure (n.): 1913, from German Rotogravur (originally, in full, Deutsche Tiefdrück Gesellschaft), said to blend two corporate names, Rotophot and Deutsche Photogravur A.G. Etymologically, the roots are Latin rota "wheel, roller" (see rotary) and French gravure "engraving" (see gravure). The process was used for printing photo sections of newspapers and magazines, so that the word came to be used for these.
rotor (n.): 1873, irregular shortening of rotator (see rotate (v.)), originally in mathematics. Mechanical sense is attested from 1903; specifically of helicopters from 1930.
Rototiller (n.): 1923, from roto-, from Latin rota "wheel" (see rotary) + tiller.
rotten (adj.): c. 1300, from a Scandinavian source akin to Old Norse rotinn "decayed," past participle of verb related to rotna "to decay," from Proto-Germanic stem *rut- (see rot (v.)). Sense of "corrupt" is from late 14c.; weakened sense of "bad" first recorded 1881. Rotten apple is from a saying traced back to at least 1528: "For one rotten apple lytell and lytell putrifieth an whole heape." The Rotten Row in London and elsewhere probably is from a different word, but of uncertain origin.
rottenness (n.): late 14c., from rotten + -ness.
rotter (n.): "person deemed objectionable on moral grounds," 1889, slang, from rot + -er (3).
Rottweiler (n.): 1907, from Rottweil, town in Württemberg, southern Germany.
rotund (adj.): 1705, from Latin rotundus "rolling, round, circular, spherical, like a wheel," from rota "wheel" (see rotary). Earlier was rotound (1610s); rotounde (early 15c.). Meaning "full-toned style of oratory" (1830) is after Horace's ore rotundo in "Poetics."
rotunda (n.): "round building," 1680s, from Italian rotonda, especially the Pantheon, from noun use of Latin rotunda, fem. of rotundus "round" (see rotund). Meaning "circular hall or room within a building" is from 1780.
rotundity (n.): 1580s, from Latin rotunditas "roundness," from rotundus "round" (see rotund).
Rotwelsch (n.): "jargon of thieves and vagabonds," 1841, from German Rotwelsch, literally "Red Welsh," from rot (see red (adj.1)) + Welsh because obscure and difficult. But the first element may be connected with Middle High German rot "beggar."
roue (n.): "debauchee," 1800, from French roué "dissipated man, rake," originally past participle of Old French rouer "to break on the wheel" (15c.), from Latin rotare "roll" (see rotary). Said to have been first applied in French c. 1720 to dissolute friends of the Duke of Orleans (regent of France 1715-23), to suggest the punishment they deserved; but probably rather from a secondary, figurative sense in French of "jaded, worn out," from the notion of "broken, run-over, beat down."
Rouen: city in northern France, Roman Rotomagus, in which the second element is Gaulish magos "field, market," and the first is roto "wheel," perhaps reflecting the Gaulish love of chariot-racing, or else it is a personal name.
rouge (n.): 1753, in cosmetic sense, "blush," from French rouge "red coloring matter," noun use of adjective "red" (12c.), from Latin rubeus, related to ruber "red" (see red). Replaced native paint in this sense. The verb is attested from 1777. Related: Rouged; rouging. The same word had been borrowed from French in Middle English with the sense "red color; red" (early 15c.).
rough (adj.): Old English ruh "rough, coarse (of cloth); hairy, shaggy; untrimmed, uncultivated," from West Germanic *rukhwaz "shaggy, hairy, rough" (source also of Middle Dutch ruuch, Dutch ruig, Old High German ruher, German rauh), from Proto-Germanic *rukhaz, from PIE *reue- (2) "to smash, knock down, tear out, dig up" (source also of Sanskrit ruksah "rough;" Latin ruga "wrinkle," ruere "to rush, fall violently, collapse," ruina "a collapse;" Lithuanian raukas "wrinkle," rukti "to shrink").

The original -gh- sound was guttural, as in Scottish loch. Sense of "approximate" is first recorded c. 1600. Of places, "riotous, disorderly, characterized by violent action," 1863. Rough draft is from 1690s. Rough-and-ready is from 1810, originally military; rough-and-tumble (1810) is from a style of free-fighting.
rough (v.): late 15c., from rough (adj.). Related: Roughed; roughing. Phrase rough it "submit to hardships" (1768) is originally nautical:
To lie rough; to lie all night in one's clothes: called also roughing it. Likewise to sleep on the bare deck of a ship, when the person is commonly advised to chuse the softest plank. [Grose, "Dictionary of the Vulgar Tongue," 1788]
To rough out "shape or plan approximately" is from 1770. To rough up "make rough" is from 1763. To rough (someone) up "beat up, jostle violently" is from 1868. The U.S. football penalty roughing was originally a term from boxing (1866).
rough (n.): c. 1200, "broken ground," from rough (adj.). Meaning "a rowdy" is first attested 1837. Specific sense in golf is from 1901. Phrase in the rough "in an unfinished or unprocessed condition" (of timber, etc.) is from 1819.
rough rider (n.): 1733, "horse-breaker," from rough (adj. or adv.) + rider. In specific military use, a non-commissioned officer in cavalry regiments, from 1802; meaning "irregular cavalryman" is attested from 1884.
rough-hewn (adj.): 1520s, originally of timber, from rough-hew (v.); see rough (adj.) + hew (v.).
rough-house (n.): 1887, "uproar, disturbance," from rough (adj.) + house (n.). The verb is first attested 1896. Related: Rough-housing.
roughage (n.): 1883, "rough grass or weeds," from rough (adj.) + -age. Meaning "coarse, bulky food" first recorded 1927.
roughen (v.): 1580s, from rough (adj.) + -en (1). Related: Roughened; roughening.
roughly (adv.): c. 1300, "ungently, violently," from rough (adj.) + -ly (2). Meaning "approximately, without precision or exactness" is from 1841.
roughneck (n.): also rough-neck, 1836, "rugged individual," from rough (adj.) + neck (n.). Original context is the Texas frontier, later adpoted to labor organization toughs. Specific sense of "oil rig worker" is recorded from 1917. Compare redneck.
roughness (n.): late 14c., from rough (adj.) + -ness.
roughshod (adj.): also rough-shod, 1680s, from rough (adj.) + shod. Originally of horses shod with the nails projecting from the shoe, to prevent slipping.
roulette (n.): 1734, "small wheel," from French roulette "gambling game played with a revolving wheel," literally "small wheel," from Old French roelete "little wheel" (12c.), formed on model of Late Latin rotella, diminutive of Latin rota "wheel" (see rotary). The game of chance so-called from 1745.
round (adj.): late 13c., from Anglo-French rounde, Old French roont (12c., Modern French rond), probably originally *redond, from Vulgar Latin *retundus (source also of Provençal redon, Spanish redondo, Old Italian ritondo), from Latin rotundus "like a wheel, circular, round," related to rota "wheel" (see rotary).

As an adverb from c. 1300; as a preposition from c. 1600. In many uses it is a shortened form of around. The French word is the source of Middle Dutch ront (Dutch rond), Middle High German runt (German rund) and similar Germanic words.

Of numbers from mid-14c., from earlier sense "full, complete, brought to completion" (mid-14c., notion of symmetry extended to that of completeness). First record of round trip is from 1844, originally of railways. Round heels attested from 1926, in reference to incompetent boxers, 1927 in reference to loose women, in either case implying an inability to avoid ending up flat on one's back.
round (n.): early 14c., "a spherical body," from round (adj.) and Old French roond. Compare Dutch rond, Danish and Swedish rund, German runde, all nouns from adjectives. Meaning "large round piece of beef" is recorded from 1650s. Theatrical sense (in phrase in the round) is recorded from 1944. Sense of "circuit performed by a sentinel" is from 1590s; that of "recurring course of time" is from 1710. Meaning "song sung by two or more, beginning at different times" is from 1520s. Golfing sense attested from 1775. Meaning "quantity of liquor served to a company at one time" is from 1630s; that of "single bout in a fight or boxing match" is from 1812; "single discharge of a firearm" is from 1725. Sense of "recurring session of meetings or negotiations" is from 1964.