rosebud (n.)
1610s, from rose (n.1) + bud (n.). Hence, "young girl in her first bloom, a debutante."
rosemary (n.)
late 14c., earlier rosmarine (c.1300), from Latin rosmarinus, literally "dew of the sea" (compare French romarin), from ros "dew" + marinus (see marine (adj.)). Perhaps so called because it grew near coasts. Form altered in English by influence of rose and Mary.

Latin ros is from PIE *ers- "to be wet" (cognates: Lithuanian rasa, Old Church Slavonic rosa "dew," Sanskrit rasah "sap, juice, fluid, essence," Hittite arszi "flows," and perhaps also Rha, Scythian name of the River Volga (see rhubarb)).
Rosetta Stone (n.)
discovered 1798 at Rosetta, Egypt; now in British Museum. Dating to 2c. B.C.E., its trilingual inscription helped Jean-François Champollion decipher Egyptian demotic and hieroglyphics in 1822, which opened the way to study of all early Egyptian records. Hence, figurative use of the term to mean "something which provides the key to previously unattainable understanding" (1902). The place name is the European form of Rashid, a name given because it was founded c.800 C.E. by Caliph Harun ar-Rashid.
rosette (n.)
"a rose-shaped ornament," especially a bunch or knot of ribbons worn as a decoration, 1790, from French rosette, diminutive of rose "rose" (see rose (n.1)).
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 (cognates: 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" (cognates: 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 (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 (adj.)
Old English ruh "rough, coarse (of cloth); hairy, shaggy; untrimmed, uncultivated," from West Germanic *rukhwaz "shaggy, hairy, rough" (cognates: 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" (cognates: 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 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.