Online Etymology Dictionary

rococo (adj.): 1836, "old-fashioned," from French rococo, apparently a humorous alteration of rocaille "shellwork, pebble-work" from Middle French roche "rock," from Vulgar Latin *rocca "stone." Specifically of furniture or architecture of the time of Louis Quatorze and Louis Quinze, from 1841. If this is correct, the reference is to the excessive use of shell designs in this lavish style. For differentiation from baroque, see baroque. The general sense of "tastelessly florid or ornate" is from 1844.
rod (n.): Old English rodd "a rod, pole," related to Old Norse rudda "club," of unknown origin. Figurative sense of "offshoot" (mid-15c.) led to Biblical meaning "scion, tribe." As an instrument of punishment, attested from mid-12c.; also used figuratively for "correction, punishment" from notion of beating someone with a stick. As a unit of measure (5.5 yards or 16.5 feet, also called perch or pole) first attested mid-15c. As a measure of area, "a square perch," from late 15c. Meaning "light-sensitive cell in a retina" is from 1866, so-called for its shape. Slang meaning "penis" is recorded from 1902; that of "gun, revolver" is from 1903.
rode: past tense of ride (q.v.).
rodent (n.): 1835, from Modern Latin rodentia, the order name, from Latin rodentem (nominative rodens), present participle of rodere "to gnaw, eat away," from PIE root *red- "to scrape, scratch, gnaw" (cf. Sanskrit radati "scrapes, gnaws," radanah "tooth;" Latin radere "to scrape;" Welsh rhathu "scrape, polish"). Uncertain connection to Old English rætt (see rat (n.)).
rodeo (n.): 1914 as public entertainment show of horse-riding skill, from earlier meaning "cattle round-up" (1834), from Spanish rodeo, "pen for cattle at a fair or market," literally "a going round," from rodear "go round, surround," related to rodare "revolve, roll," from Latin rotare "go around" (see rotary).
Roderick: masc. proper name, from Old High German Hroderich, literally "ruling in fame," from hruod- "fame, glory" + Proto-Germanic *rikja "rule" (see rich). Italian and Spanish Rodrigo, Russian Rurik are from German.
rodomontade (n.): 1610s, "vain boasting like that of Rodomonte," character in Ariosto's "Orlando Furioso" (earlier rodomontado, 1590s). The name means literally "one who rolls (away) the mountain" in dialectal Italian.
roe (n.1): "fish eggs," c.1400, from Proto-Germanic *khrugna (cf. Old Norse hrogn, Flemish rog, Middle Low German and Middle Dutch roge, Old High German rogo "roe"), from PIE *qreq- "spawn" (cf. Lithuanian kurkle, Russian krjak "spawn of frogs"). Exact relations of the Germanic words are uncertain.
roe (n.2): "small deer," Old English ra, from raha, from Proto-Germanic *raikhon (cf. Old Norse ra, Dutch ree, Old High German reho, German Reh "doe"), perhaps from PIE root *rei- "streaked, spotted."
roebuck (n.): c.1400, from roe (n.2) + buck (n.1).
roentgen: 1896, in Roentgen rays "X-rays," in recognition of German physicist Wilhem Conrad Röntgen (1845-1923), who discovered X-rays in 1895. As a unit of exposure to radiation, it is attested from 1922, proposed in French in 1921.
rofl: by 1993, online chat abbreviation for rolling on the floor laughing.
rogation (n.): late 14c., from Latin rogationem (nominative rogatio), noun of action from past participle stem of rogare "to ask," apparently an image, literally "to stretch out (the hand)," from PIE *rog-, 0-grade form of root *reg- "move in a straight line" (see regal).

Rogation days were the Monday, Tuesday and Wednesday before Ascension Day, a time for processions round fields blessing crops and praying for good harvest, also blessing the boundary markers of each parish. Discouraged by Protestants as superstitious, but continued or revived in modified form as beating the bounds.
Roger: masc. proper name, from Old French Rogier, from Old High German Hrotger, literally "famous with the spear," from hruod- "fame, glory" + ger "spear." As a generic name for "a person," attested from 1630s. Slang meaning "penis" was popular c.1650-c.1870; hence the slang verb sense of "to copulate with (a woman)," attested from 1711. The use of the word in radio communication to mean "yes, I understand" is attested from 1941, from the U.S. military phonetic alphabet word for the letter -R-, in this case an abbreviation for "received." Said to have been used by the R.A.F. since 1938. The Jolly Roger pirate flag is first attested 1723, of unknown origin; jolly here has its otherwise obsolete Middle English sense "high-hearted, gallant."
Roget: in reference to the "Thesaurus of English Words and Phrases" published 1852 by English physician and philologist Peter Mark Roget (1779-1869).
rogue (n.): 1560s, "idle vagrant," perhaps a shortened form of roger (with a hard -g-), thieves' slang for a begging vagabond who pretends to be a poor scholar from Oxford or Cambridge, perhaps from Latin rogare "to ask." Another theory traces it to Celtic (cf. Breton rog "haughty"); OED says, "There is no evidence of connexion with F. rogue 'arrogant.' " Rogue's gallery "police collection of mug shots" is attested from 1859.
roguish (adj.): 1570s, from rogue + -ish. Related: Roguishly; roguishness.
Rohypnol (n.): 1995, trade name for a powerful insomnia drug.
roil (v.): 1590, probably from Middle French rouiller "to rust, make muddy," from Old French rouil "mud, rust," from Vulgar Latin *robicula, from Latin robigo "rust" (see robust). Middle English roil meant "to roam or rove about." Related: Roiled; roiling.
roister (v.): 1580s, from an obsolete noun roister "noisy bully" (1550s), from Middle French ruistre "ruffian," from Old French ruste "rough country fellow," from Latin rusticus (see rustic). Related: Roistered; roistering.
Roland: masc. proper name, from French, from Old High German Hrodland, literally "(having a) famous land." As legendary nephew of Charlemagne, celebrated in "Chanson de Roland," c.1300.
role (n.): "part or character one takes," c.1600, from French rôle "part played by a person in life," literally "roll (of paper) on which an actor's part is written," from Old French rolle (see roll (n.)). Role model first attested 1957.
roleplay: also role play, as a verb, by 1961; see from role + play (v.).
Rolex (n.): proprietary name of a make of watches, trademark reg. 1908 by German businessman Hans Wilsdorf, with Wilsdorf & Davis, London. Invented name. Company moved out of Britain 1912 for tax purposes and now is headquartered in Geneva.
Rolf: masc. proper name, introduced in England by the Normans, from Old Norse Hrolfr, related to Old High German Hrodulf, literally "wolf of fame" (see Rudolph). Rolfing (1972) as a deep massage technique is named for U.S. physiotherapist Ida P. Rolf (1897-1979), and first attested 1958, as Rolf Technique.
roll (n.): early 13c., "rolled-up piece of parchment or paper," from Old French rolle, from Medieval Latin rotulus "a roll of paper," from Latin rotula "small wheel," diminutive of rota "wheel." Meaning "dough which is rolled before baking" is first recorded 1580s. Meaning "quantity of paper money" is from 1846; sense of "quantity of (rolled) film" is from 1890. Meaning "act of sexual intercourse" is attested from 1942.
roll (v.): c.1300 in intransitive sense of "to move by rotating;" late 14c. as "to move (something) by turning it over and over," from roll (n.).
The rollyng stone neuer gatherth mosse. [John Heywood, "A dialogue conteinying the nomber in effect of all the proverbes in the Englishe tongue," 1546]
Of eyes, from 1510s. Of a movie camera, "to start filming," from 1938. Sense of "to rob a stuporous drunk" is from 1873, from the action required to get to his pockets. To roll with the punches is a metaphor from boxing (1940). Rolling pin is recorded from late 15c. Heads will roll is a Hitlerism:
If our movement is victorious there will be a revolutionary tribunal which will punish the crimes of November 1918. Then decapitated heads will roll in the sand. [1930]
roll call (n.): 1775; see roll (n.) + call.
rollback (n.): "reduction," 1942, American English, from roll (v.) + back (adv.).
roller (n.): early 15c., "rolling pin," agent noun from roll (v.). Meaning "hair-curler" is attested from 1795. Religious holy roller is attested from 1842, American English.
Rollerblade (n.): 1985, a registered proprietary name in U.S., from roller + blade (n.).
rollercoaster (n.): also (and originally) roller coaster, by 1884, perhaps mid-1870s, from roller + coaster.
rollerskate (n.): also roller-skate, 1861, American English, from roller + skate (n.). The verb is from 1885. Related: Rollerskated; rollerskating. Derived Roller derby is attested from 1936.
rollicking (adj.): 1811, present participle adjective from rollick "to frolic, sport" (though this does not appear in print until 1826), which is perhaps a blend of roll (v.) and frolic.
rollout (n.): 1957, originally of airplanes, from roll (v.) + out (adv.).
rollover (n.): also roll over "an overturning," 1945; see roll (v.) + over. Economic verbal sense of "reinvest" is from 1957.
Rolls-Royce: registered 1908 as trademark, named for designers C.S. Rolls (1877-1910) and Sir Henry Royce (1863-1933). Extended 1916 to any product of high quality. Shortened form Rolls first attested 1928.
Rolodex (n.): 1958, said to be from rolling + index.
roly-poly (adj.): "short and stout," 1820, probably a varied reduplication of roll (v.). As a noun, it was used as the name of various ball games from 1713, and it was used as early as 1610s in the sense of "rascal."
Rom: "male gypsy," 1841, see Romany.
romaine (adj.): type of lettuce, 1876, from French romaine (in laitue romaine, literally "Roman lettuce"), from fem. of Old French romain "Roman," from Latin Romanus "Roman." Perhaps so called because of the lettuce's introduction into France (by Bureau de la Rivière, chamberlain of Charles V and VI) at the time of the Avignon papacy (1309-77).
Roman: Old English, from Latin Romanus "of Rome, Roman," from Roma "Rome" (see Rome). The Old English word was romanisc, which yielded Middle English Romanisshe.

As a type of numeral (opposed to Arabic) it is attested from 1728; as a type of lettering (based on Roman inscriptions, opposed to Gothic, or black letter, and italic) it is recorded from 1510s. Roman nose is from 1620s. Roman candle recorded from 1834. Roman Catholic is attested from c.1600, originally a conciliatory formation from the time of the Spanish Match, in place of Romanist, Romish which by that time had the taint of insult in Protestant England.
roman (n.): "a novel," 1765, from French roman, from Old French romanz (see romance); roman à clef, novel in which characters represent real persons, literally "novel with a key" (French), first attested in English 1893.
Roman holiday (n.): "occasion on which entertainment or profit is derived from injury or death," 1860, originally in reference to holidays for gladiatorial combat; the expression seems to be entirely traceable to an oft-quoted passage on a dying barbarian gladiator from the fourth canto (1818) of Byron's "Childe Harold's Pilgrimage":
But where his rude hut by the Danube lay
There were his young barbarians all at play,
There was their Dacian mother. He, their sire,
Butcher'd to make a Roman holiday!
romance (n.): c.1300, "story of a hero's adventures," also (early 14c.), "vernacular language of France" (as opposed to Latin), from Old French romanz "verse narrative," originally an adverb, "in the vernacular language," from Vulgar Latin *romanice scribere "to write in a Romance language" (one developed from Latin instead of Frankish), from Latin Romanicus "of or in the Roman style," from Romanus "Roman" (see Roman). The connecting notion is that medieval vernacular tales were usually about chivalric adventure. Literary sense extended by 1660s to "a love story." Extended 1610s to other modern languages derived from Latin (Spanish, Italian, etc.). Meaning "adventurous quality" first recorded 1801; that of "love affair, idealistic quality" is from 1916.
romance (v.): "court as a lover," 1938, from romance (n.). Related: Romanced; romancing.
Romanesque (adj.): 1715, originally "descended from Latin" (cf. romance), later "architectural style in Europe between Roman and Gothic periods" (1819), from Roman, influenced by French romanesque, from Late Latin Romanice "in Vulgar Latin" (see romance).
Romania: Eastern European nation, name taken officially in 1861 at the union of Wallachia and Moldavia, from Latin Romani "people from Rome," which was used to describe the descendants of colonists there from Roman times.
Romanic (adj.): "pertaining to Rome or the Roman people," 1708, originally in reference to languages descended from Latin, from Latin Romanicus, from Romanus "Roman" (see Roman).
Romano: strong-tasting hard cheese, 1908, from Italian, literally "Roman."