Online Etymology Dictionary

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 (cf. Old Frisian reinboga, Old Norse regnbogi, Swedish regenbåge, Dutch regenboog, German Regenbogen). Rainbow trout (1876, American English) so called for its resplendent colors.
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.).
raindrop (n.): Old English rendropa; see rain (n.) + drop (n.).
rainfall (n.): also rain-fall, "amount of precipitation that falls as rain," 1839, from rain (n.) + fall (n.).
rainmaker (n.): also rain-maker, 1775, in reference to American Indian tribal magicians, from rain (n.) + agent noun of make (v.).
rainproof (adj.): also rain-proof, 1788, from rain (n.) + proof (n.).
rainstorm (n.): 1804, from rain (n.) + storm (n.).
rainwater (n.): Old English renwæter; see rain (n.) + water (n.1).
rainy (adj.): Old English renig; see rain (n.) + -y (2).
raise (n.): "act of raising or lifting," 1530s, from raise (v.). Meaning "an increase in amount or value" is from 1728. Meaning "increase in salary or wages" is from 1898, chiefly American English (British preferring rise). Earliest attested use (c.1500) is in obsolete sense of "a levy."
raise (v.): c.1200, "cause a rising of; lift upright, set upright; build, construct," from a Scandinavian source, e.g. Old Norse reisa "to raise," from Proto-Germanic *raizjan (cf. Gothic ur-raisjan, Old English ræran "to rear;" see rear (v.)), causative of root *ris- "to rise" (see rise (v.)). At first sharing many senses with native rear (v.).

Meaning "make higher" is from c.1300 in the physical sense, as is that of "restore to life." Of the voice, from late 14c. Meaning "increase the amount of" is from c.1500; from 1530s of prices, etc. Meaning "to bring up" (a question, etc.) is from 1640s. Card-playing sense is from 1821. Meaning "promote the growth of" (plants, etc.) is from 1660s; sense of "foster, rear, bring up" (of children) is from 1744. Meaning "to elevate" (the consciousness) is from 1970. Related: Raised; raising.
raisin (n.): "dried sweet grape," c.1300, from Anglo-French raycin (late 13c.), Old French raisin "grape; raisin," from Vulgar Latin *racimus, alteration of Latin racemus "cluster of grapes or berries" (also source of Spanish racimo, Italian racemo), probably from the same ancient lost Mediterranean language that gave Greek rhax (genitive rhagos) "grape, berry." Dutch razun also is from French; German Rosine is from an Old French variant form.
raison d'etat (n.): from French raison d'état "reason of state," thus "convenience of the government."
raison d'etre (n.): "excuse for being," 1864, first recorded in letter of J.S. Mill, from French raison d'être, literally "rational grounds for existence."
raisonne (adj.): "arranged logically," 1777, from French raisonné "reasoned," past participle of raisonner "to reason," from raison (see reason (n.)).
Raj (n.): British rule in India, 1859, from Hindi raj "rule, dominion, kingdom" (see rajah).
rajah (n.): also raja, "king or prince in India," 1550s, from Hindi, from Sanskrit rajan "king," related to raj "kingdom, kingship," rajati "he rules," and cognate with Latin rex, Old Irish rig "king" (see regal). Related: Rajput, "member of the ruling caste in northern India" (1590s), from Sanskrit rajaputrah "prince," literally "king's son," from putrah "son, boy" (cf. puerile).
rake (n.1): "toothed tool for drawing or scraping things together," Old English raca "rake," earlier ræce, from Proto-Germanic *rak- "gather, heap up" (cf. Old Norse reka "spade, shovel," Old High German rehho, German Rechen "a rake," Gothic rikan "to heap up, collect"), from PIE *reg- (1) "move in a straight line" (cf. Greek oregein "to reach, stretch out," Latin regere "direct, rule; keep straight, guide;" see regal), perhaps via its action, or via the notion of "implement with straight pieces of wood" [Watkins].
rake (v.): mid-13c., "clear (rubbish, grass, etc.) by raking; gather (grain) by raking," from rake (n.1), or from a lost Old English verb related to it, or from a similar Scandinavian source (cf. Swedish raka, Danish rage "rake"). Of gunfire from 1630s. Related: Raked; raking. To rake in money or something like it is from 1580s.
rake (n.2): "debauchee; idle, dissolute person," 1650s, shortening of rakehell. Hogarth's "Rake's Progress" engravings were published in 1735.
rakehell (n.): 1540s, possibly an alteration (by association with rake (n.1) and Hell) of Middle English rakel (adj.) "hasty, rash, headstrong," probably from raken "to go, proceed," from Old English racian "to go forward, move, hasten," of unknown origin. Cf. rakeshame (n.) "one who lives shamefully" (1590s).
rakish (adj.): 1706, "debauched, disreputable," from rake (n.2) + -ish. Related: Rakishly; rakishness.

The meaning "smart, jaunty, dashing" (1824) is said to be a different word, probably from rake "slant, slope" (1620s), used especially in reference to a ship's hull or sails, of uncertain origin, perhaps from Scandinavian (cf. Old Swedish raka "project, reach;" Danish rage "protrude, project") related to Old English reccan "stretch." "The piratical craft of former times were distinguished for their rakish build" ["Century Dictionary"].
Raleigh: city in North Carolina, U.S., founded 1792 and named for Sir Walter Raleigh (1552-1618).
rally (n.): 1650s, originally in the military sense of "a regrouping for renewed action after a repulse," from rally (v.1). Sense of "mass meeting to stir enthusiasm" first attested 1840, American English. Sense of "gathering of automobile enthusiasts" is from 1932, from French rallye, itself from the English noun. Sports sense of "long series of hits" in tennis, etc., is from 1881, earlier "series of back-and-forth blows in a boxing match" (1829).
rally (v.1): "bring together," c.1600, from French rallier, from Old French ralier "reassemble, unite again," from re- "again" (see re-) + alier "unite" (see ally (v.)). Intransitive meaning "pull together hastily, recover order, revive, rouse" is from 1660s. Related: Rallied; rallying. Rally round the flag (1862) is a line from popular American Civil War song "Battle Cry of Freedom."
rally (v.2): "make fun of, tease," 1660s, from French railler "to rail, reproach" (see rail (v.)).
Ralph: masc. proper name, shortened from Radulf, from Old Norse Raðulfr (Old English Rædwulf), literally "wolf-counsel," from rað "counsel" (see read (n.)) + ulfr "wolf" (see wolf (n.)). The "Century Dictionary" also lists it as English printers' slang for "An alleged or imagined evil spirit who does mischief in a printing house."
ram (v.): "to beat with a heavy implement," c.1300, from ram (n.). Related: Rammed; ramming.
ram (n.): Old English ramm "male sheep," also "battering ram" and the zodiac sign; earlier rom "male sheep," a West Germanic word (cf. Middle Low German, Middle Dutch, Dutch, Old High German ram), of unknown origin. Perhaps [Klein] connected with Old Norse rammr "strong," Old Church Slavonic ramenu "impetuous, violent."
RAM (n.): 1957, acronym for random access memory (computerese).
Rama: incarnation of Vishnu, from Sanskrit Ramah, literally "lovely," from stem of ramate "stands still, rests, is pleased."
ramada (n.): "arbor, porch," 1869, from American Spanish ramada "tent, shelter," from Spanish ramada "an arbor," from rama "branch," from Vulgar Latin *rama, collective of Latin ramus "branch" (see ramus).
Ramadan (n.): ninth month of the Muslim year, 1590s, from Arabic Ramadan (Turkish and Persian ramazan), originally "the hot month," from ramida "be burnt, scorched" (cf. Mishnaic Hebrew remetz "hot ashes, embers"). In the Islamic lunar calendar, it passes through all seasons in a cycle of about 33 years, but evidently originally it was a summer month.
ramble (v.): mid-15c., perhaps frequentative of romen "to walk, go" (see roam), perhaps via romblen (late 14c.) "to ramble." The vowel change perhaps by influence of Middle Dutch rammelen, a derivative of rammen "copulate," "used of the night wanderings of the amorous cat" [Weekley]. Meaning "to talk or write incoherently" is from 1630s. Related: Rambled; rambling.
ramble (n.): "a roving or wandering," 1650s, from ramble (v.).
rambler (n.): 1620s, agent noun from ramble (v.).
rambling (adj.): 1623, present participle adjective from ramble (v.).
Rambo: used allusively from 1985, in reference to John Rambo, hero of David Morrell's novel "First Blood" (1972), popularized as portrayed by Sylvester Stallone in Hollywood movie version (1982), a U.S. Vietnam veteran, "macho and self-sufficient, and bent on violent retribution" [OED]. The family name is an old one in New Jersey and Pennsylvania, originally Swedish, sometimes said to represent Swedish place name Ramberget, or to be from French Huguenots who took refuge in Sweden.
rambunctious (adj.): 1859, earlier rumbunctious, 1830, probably altered (by influence of ram) from rumbustious.
ramekin: 1706, from French ramequin (late 17c.), said to be from a Germanic source (cf. Middle Low German rom "cream"), from Proto-Germanic *rau(g)ma-, of uncertain origin.
ramification (n.): 1670s, "a branching out," from French ramification, from ramifier (see ramify). Transferred sense of "outgrowth, consequence" first recorded 1755. Related: Ramifications.
ramify (v.): early 15c., "branch out," from Middle French ramifier (early 14c.), from Medieval Latin ramificare "to form branches," from Latin ramus "branch" (see ramus) + root of facere "to make" (see factitious). Related: Ramified; ramifying.
ramjet (n.): 1942, from ram (v.) + jet (n.).
rammy (adj.): c.1600, from ram (n.) + -y (2). Related: Ramminess.
ramp (n.1): 1778, "slope," from French rampe, back-formation from Old French verb ramper "to climb, scale, mount;" see ramp (v.). Meaning "road on or off a major highway" is from 1952, American English.
ramp (n.2): "rude, boisterous girl or woman," mid-15c., perhaps from ramp (v.). Cf. romp in Johnson's Dictionary (1755): "a rude, awkward, boisterous, untaught girl."
ramp (v.): c.1300, "to climb; to stand on the hind legs" (of animals), from Old French ramper "to climb, scale, mount" (12c., in Modern French "to creep, crawl"), perhaps from Frankish *rampon "to contract oneself" (cf. Old High German rimpfan "to wrinkle," Old English hrimpan "to fold, wrinkle"), via notion of the bodily contraction involved in climbing [Klein], from Proto-Germanic *hrimp- "to contract oneself." Related: Ramped; ramping.
rampage (v.): 1715, in Scottish, probably from Middle English verb ramp "rave, rush wildly about" (c.1300), especially of beasts rearing on their hind legs, as if climbing, from Old French ramper (see ramp (n.1), also cf. rampant). Related: Rampaged; rampaging.