Online Etymology Dictionary

Rafflesia (n.): genus of Malaysian plants, 1820, named for Sir T. Stamford Raffles (1781-1826), British governor of Sumatra, who introduced it to the West, + abstract noun ending -ia. He reports the native name was petimum sikinlili "Devil's betel-box."
raft (n.1): "floating platform," late 15c., originally "rafter" (c. 1300), from a Scandinavian source such as Old Norse raptr "log" (Old Norse -pt- pronounced as -ft-), related to Middle Low German rafter, rachter "rafter" (see rafter).
raft (n.2): "large collection," 1830, variant of raff "heap, large amount," from Middle English raf (compare raffish, riffraff); form and sense associated with raft (n.1).
raft (v.): 1680s, from raft (n.1). Related: Rafted; rafting.
rafter (n.): "sloping timber of a roof," Old English ræftras (West Saxon), reftras (Mercian), both plural, related to Old Norse raptr "log," from Proto-Germanic *raf-tra-, from PIE *rap-tro-, from root *rep- "stake, beam."
rag (n.): scrap of cloth, early 14c., probably from Old Norse rögg "shaggy tuft," earlier raggw-, or possibly from Old Danish rag (see rug), or a back-formation from ragged, It also may represent an unrecorded Old English cognate of Old Norse rögg. In any case, from Proto-Germanic *rawwa-, from PIE root *reue- (2) "to smash, knock down, tear up, uproot" (see rough (adj.)).

As an insulting term for "newspaper, magazine" it dates from 1734; slang for "tampon, sanitary napkin" is attested from 1930s (on the rag "menstruating" is from 1948). Rags "personal clothing" is from 1855 (singular), American English. Rags-to-riches "rise from poverty to wealth" is attested by 1896. Rag-picker is from 1860; rag-shop from 1829.
rag (v.): "scold," 1739, of unknown origin; perhaps related to Danish dialectal rag "grudge." Related: Ragged; ragging. Compare bullyrag, ballarag "intimidate" (1807).
rag-bag (n.): 1820, from rag (n.1) + bag (n.). Figurative sense of "motley collection" is first recorded 1864.
rag-doll (n.): child's plaything, 1776 (from 1757 as "a dressed-up woman"), from rag (n.1) + doll (n.). Rag-baby attested from 1798. Shakespeare has babe of clowts (i.e. "clouts"), 1590s.
raga (n.): 1788, from Sanskrit raga-s "harmony, melody, mode in music," literally "color, mood," related to rajyati "it is dyed," from PIE *reg- (3) "to dye" (source also of Greek rhegos "blanket, rug").
ragamuffin (n.): mid-14c., "demon," also in surnames (Isabella Ragamuffyn, 1344), from Middle English raggi "ragged" ("rag-y"?) + fanciful ending (or else second element is Middle Dutch muffe "mitten"). Or, as Johnson has it, "From rag and I know not what else." Ragged was used of the devil from c. 1300 in reference to "shaggy" appearance. Raggeman was used by Langland as the name of a demon, and compare Old French Ragamoffyn, name of a demon in a mystery play. Sense of "dirty, disreputable boy" is from 1580s. Compare in the same sense ragabash (c. 1600).
rage (n.): c. 1300, "madness, insanity; fit of frenzy; anger, wrath; fierceness in battle; violence of storm, fire, etc.," from Old French rage, raige "spirit, passion, rage, fury, madness" (11c.), from Medieval Latin rabia, from Latin rabies "madness, rage, fury," related to rabere "be mad, rave" (compare rabies, which originally had this sense), from PIE *rebh- "violent, impetuous" (source also of Old English rabbian "to rage"). Similarly, Welsh (cynddaredd) and Breton (kounnar) words for "rage, fury" originally meant "hydrophobia" and are compounds based on the word for "dog" (Welsh ci, plural cwn; Breton ki). In 15c.-16c. it also could mean "rabies." The rage "fashion, vogue" dates from 1785.
rage (v.): mid-13c., "to play, romp," from rage (n.). Meanings "be furious; speak passionately; go mad" first recorded c. 1300. Of things from 1530s. Related: Raged; raging.
ragged (adj.): "rough, shaggy," c. 1300, past participle adjective as though from a verb form of rag (n.). Compare Latin pannosus "ragged, wrinkly," from pannus "piece of cloth." But the word might reflect a broader, older meaning; perhaps from or reinforced by Old Norse raggaðr "shaggy," via Old English raggig "shaggy, bristly, rough" (which, Barnhart writes, "was almost surely developed from Scandinavian"). Of clothes, early 14c.; of persons, late 14c. To run (someone) ragged is from 1915. Related: Raggedly; raggedness.
raggedy (adj.): 1845, U.S. Southern, from ragged + -y (2). Raggedy Ann stories first published 1918, character created by U.S. illustrator Johnny Gruelle (1880-1938). The tangle of tales about the origin of the doll and the name probably are mostly invention, sorrow's grieving-shrine for Marcella Gruelle (1902-1915), best left alone.
raggedy-ass (adj.): by 1930, from raggedy + ass (n.2).
raghead (n.): insulting term for "South Asian or Middle Eastern person," 1910, from rag (n.) + head (n.); in reference to turbans, etc.
raglan (n.): type of overcoat, 1863, named for British general Lord Raglan (1788-1855), commander of British forces in the Crimean War. The name is from a place in Wales.
Ragnarok (n.): in Norse mythology, the last battle of the world, in which gods and men will be destroyed by monsters and darkness, 1770, from Old Norse ragna, genitive of rögn "gods" + rök "destined end" or rökr "twilight." Also see Gotterdammerung.
ragout (n.): "highly seasoned meat and vegetable stew," 1650s, from French ragoût (mid-17c.), from Middle French ragoûter "awaken the appetite," from Old French re- "back" (see re-) + à "to" + goût "taste," from Latin gustum (nominative gustus); see gusto.
ragtag (n.): also rag-tag, "ragged people collectively," 1820, from rag (n.) + tag (n.); originally in expression rag-tag and bobtail "the rabble" (tag-rag and bobtail is found in 1650s), with bobtail an old 17c. word for "cur." Tag and rag was "very common in 16-17th c." [OED]
ragtime (n.): also rag-time, "syncopated, jazzy piano music," 1897, perhaps from rag "dance ball" (1895, American English dialect), or a shortening of ragged, in reference to the syncopated melody. Rag (n.) "ragtime dance tune" is from 1899.
If rag-time was called tempo di raga or rague-temps it might win honor more speedily. ... What the derivation of the word is[,] I have not the faintest idea. The negroes call their clog-dancing "ragging" and the dance a "rag." [Rupert Hughes, Boston "Musical Record," April 1900]

Conceive the futility of trying to reduce the intangible ragness to a strict system of misbegotten grace notes and untimely rests! In attempting to perfect, and simplify, art is destroying the unhampered spirit in which consists the whole beauty of rag-time music. The very essence of rag-time is that it shall lack all art, depending for the spirit to be infused more upon the performer than upon the composer himself. ["Yale Literary Magazine," June, 1899]

Her first "rag-time" was "The Bully," in which she made great sport by bringing a little coloured boy on the stage with her. Miss [May] Irwin says the way to learn to sing "rag-time" is to catch a negro and study him. [Lewis C. Strang, "Famous Actresses of the Day in America," Boston, 1899]
ragtop (n.): "convertible car," 1954, from rag (n.) + top (n.1).
ragweed (n.): 1790, from ragged + weed (n.); so called from shape of the leaves. Applied to a different plant (ragwort) from 1650s.
ragwort (n.): mid-15c., from ragged, in reference to the appearance of the leaves, + wort.
rah: in cheers, 1870, a shortening of hurrah. Adjective rah-rah is attested from 1907, originally indicating college life generally, later enthusiastic cheerleading.
Rahab: name of a Biblical monster, from Hebrew rahab, literally "storming, against, impetuous," from rahabh "he stormed against" (compare Arabic rahiba "he feared, was alarmed").
raid (n.): early 15c., "mounted military expedition," Scottish and northern English form of rade "a riding, journey," from Old English rad "a riding, ride, expedition, journey; raid," (see road). The word died out by 17c., but was revived by Scott ("The Lay of the Last Minstrel," 1805), ("Rob Roy," 1818), with extended sense of "attack, foray."
raid (v.): "take part in a raid," 1785 (implied in raiding), from raid (n.). Related: Raided; raiding. Also see raider.
raider (n.): 1863, agent noun from raid (v.). A word from the American Civil War.
rail (n.1): "horizontal bar passing from one post or support to another," c. 1300, from Old French reille "bolt, bar," from Vulgar Latin *regla, from Latin regula "straight stick," diminutive form related to regere "to straighten, guide" (see regal). Used figuratively for thinness from 1872. To be off the rails in a figurative sense is from 1848, an image from the railroads. In U.S. use, "A piece of timber, cleft, hewed, or sawed, inserted in upright posts for fencing" [Webster, 1830].
rail (n.2): "small wading bird," mid-15c., from Old French raale (13c.), related to râler "to rattle," of unknown origin, perhaps imitative of its cry.
rail (v.1): "complain," mid-15c., from Middle French railler "to tease or joke" (15c.), perhaps from Old Provençal ralhar "scoff, to chat, to joke," from Vulgar Latin *ragulare "to bray" (source also of Italian ragghiare "to bray"), from Late Latin ragere "to roar," probably of imitative origin. See rally (v.2). Related: Railed; railing.
rail (v.2): "fence in with rails," late 14c., from rail (n.1). Related: Railed; railing.
rail-splitter (n.): 1853, from rail (n.1) + agent noun from split (v.). Usually with reference to or suggestion of U.S. president Abraham Lincoln, as it figured in his political biography.
railing (n.): "construction in which rails form an important part," early 15c., verbal noun from rail (v.2). Technically, railings (late 15c.) are horizontal, palings are vertical.
raillery (n.): "good-humored ridicule," 1650s, from rail (v.) + -ery, or perhaps from French raillerie, from Middle French railler "to tease" (see rail (v.1)).
railroad (n.): 1757, from rail (n.1) + road. Originally "road laid with rails for heavy wagons (in mining)." The process itself (but not the word) seems to have been in use by late 17c. Application to passenger and freight trains dates from 1825, though tending to be replaced in this sense in England by railway.
railroad (v.): "to convict quickly and perhaps unjustly," 1873, American English, from railroad (n.).
A person knowing more than might be desirable of the affairs, or perhaps the previous life of some powerful individual, high in authority, might some day ventilate his knowledge, possibly before a court of justice; but if his wisdom is railroaded to State's prison, his evidence becomes harmless. ["Wanderings of a Vagabond," New York, 1873]
Related: Railroaded; railroading. An earlier verb sense was "to have a mania for building railroads" (1847).
railroading (n.): 1842, "travel by rail," from railroad (n.). As "business of running railways" from 1882.
railway (n.): 1812 in modern sense, from rail (n.1) + way (n.). Earlier used of any sort of road on which rails (originally wooden) were laid for easier transport (1776).
raiment (n.): c. 1400, "clothing, vesture" (archaic), shortening of arayment "clothing" (late 14c.), from Anglo-French araiement, from Old French areement, from areer "to array" (see array (v.)).
rain (n.): Old English regn "rain," from Proto-Germanic *regna- (source also of Old Saxon regan, Old Frisian rein, Middle Dutch reghen, Dutch regen, German regen, Old Norse regn, Gothic rign "rain"), with no certain cognates outside Germanic, unless it is from a presumed PIE *reg- "moist, wet," which may be the source of Latin rigare "to wet, moisten" (see irrigate). Rain dance is from 1867; rain date in listings for outdoor events is from 1948. To know enough to come in out of the rain (usually with a negative) is from 1590s. Rainshower is Old English renscur.
rain (v.): Old English regnian, usually contracted to rinan; see rain (n.), and compare Old Norse rigna, Swedish regna, Danish regne, Old High German reganon, German regnen, Gothic rignjan. Related: Rained; raining. Transferred and figurative use of other things that fall as rain (blessings, tears, etc.) is recorded from c. 1200.

To rain on (someone's) parade is attested from 1941. Phrase to rain cats and dogs is attested from 1738 (variation rain dogs and polecats is from 1650s), of unknown origin, despite intense speculation. One of the less likely suggestions is pets sliding off sod roofs when the sod got too wet during a rainstorm. (Ever see a dog react to a rainstorm by climbing up on an exposed roof?) Probably rather an extension of cats and dogs as proverbial for "strife, enmity" (1570s).
rain forest (n.): 1899, apparently a loan-translation of German Regenwald, coined by A.F.W. Schimper for his 1898 work "Pflanzengeographie."
rain-cloud (n.): also raincloud, 1800, from rain (n.) + cloud (n.).
rain-out (n.): also rain out, rainout, 1947, from rain (v.) + out (adv.). Of baseball games, to be rained out is attested from 1928.
rainbow (n.): Old English renboga; see rain (n.) + bow (n.). Common Germanic compound (Old Frisian reinboga, Old Norse regnbogi, Swedish regenbåge, Dutch regenboog, German Regenbogen). Rainbow trout (1876, American English) so called for its resplendent colors. Old English also had scurboga "shower-bow."
raincheck (n.): also rain-check, rain check, 1884; see rain (n.) + check (n.1). Originally of tickets to rained-out baseball games.
raincoat (n.): also rain-coat, 1821, from rain (n.) + coat (n.).