Online Etymology Dictionary

R: In a circle, meaning "registered (trademark)," first incorporated in U.S. statues 1946. R&R "rest and relaxation," first recorded 1953, American English; R&B "rhythm and blues" (type of popular music) first attested 1949, American English.
If all our r's that are written are pronounced, the sound is more common than any other in English utterance (over seven per cent.); the instances of occurrence before a vowel, and so of universal pronunciation, are only half as frequent. There are localities where the normal vibration of the tip of the tongue is replaced by one of the uvula, making a guttural trill, which is still more entitled to the name of "dog's letter" than is the ordinary r; such are considerable parts of France and Germany; the sound appears to occur only sporadically in English pronunciation. [Century Dictionary]

The moment we encounter the added r's of purp or dorg in our reading we know that we have to do with humor, and so with school-marm. The added consonants are supposed to be spoken, if the words are uttered, but, as a matter of fact, they are less often uttered than seen. The words are, indeed, largely visual forms; the humor is chiefly for the eye. [Louise Pound, "The Humorous 'R,'" "American Mercury," October 1924]
She goes on to note that in British humorous writing, -ar "popularly indicates the sound of the vowel in father" and formations like larf (for laugh) "are to be read with the broad vowel but no uttered r." She also quotes Henry James on the characteristic prominence of the medial -r- sound (which tends to be dropped in England and New England) in the speech of the U.S. Midwest, "under some strange impulse received toward consonantal recovery of balance, making it present even in words from which it is absent, bringing it in everywhere as with the small vulgar effect of a sort of morose grinding of the back teeth."
R.A.F.: also RAF, initialism (acronym) for Royal Air Force, founded 1918 by consolidation of Royal Flying Corps and Royal Naval Air Service.
R.E.M.: also REM, 1957, initialism (acronym) for rapid eye movement.
R.O.T.C.: also ROTC, 1916, American English, initialism (acronym) for Reserve Officers' Training Corps, established as part of the National Defense Act of 1916.
R.S.V.P.: also RSVP, c. 1845, from French initialism (acronym) of répondez, s'il vous plait "reply, if you please," as it might have been written on a letter or envelope.
Ra: "hawk-headed sovereign sun god of Egyptian mythology," from Egyptian R' "sun, day."
Rabat: Moroccan capital, from Arabic ar-ribat, from ribat "fortified monastery."
rabbet (n.): "rectangular groove cut out of the edge of a piece of wood or stone so that it may join by lapping with others," late 14c., from Old French rabat "a recess in a wall, a lower section," literally "a beating down," a back-formation from rabattre "to beat down, beat back" (see rebate (v.)). The verb is attested from mid-15c. (implied in rabetynge).
rabbi (n.): "Jewish doctor of religious law," late 15c. (in Old English in biblical context only; in Middle English also as a title prefixed to personal names), from Late Latin rabbi, from Greek rhabbi, from Mishnaic Hebrew rabbi "my master," from rabh "master, great one," title of respect for Jewish doctors of law + -i, first person singular pronominal suffix. From Semitic root r-b-b "to be great or numerous" (compare robh "multitude;" Aramaic rabh "great; chief, master, teacher;" Arabic rabba "was great," rabb "master").
rabbinate (n.): 1702, from rabbin "rabbi" (see rabbinical) + -ate (1).
rabbinical (adj.): 1620s, earlier rabbinic (1610s); see Rabbi + -ical. The -n- is perhaps via rabbin "rabbi" (1520s), an alternative form, from French rabbin, from Medieval Latin rabbinus (also source of Italian rabbino, Spanish and Portuguese rabino), perhaps from a presumed Semitic plural in -n, or from Aramaic rabban "our teacher," "distinguishing title given to patriarchs and the presidents of the Sanhedrin since the time of Gamaliel the Elder" [Klein], from Aramaic plural of noun use of rabh "great."
rabbit (n.): late 14c., "young of the coney," from Walloon robète or a similar French dialect word, diminutive of Flemish or Middle Dutch robbe "rabbit," of unknown origin. "A Germanic noun with a French suffix" [Liberman]. The adult was a coney (q.v.) until 18c.
Zoologically speaking, there are no native rabbits in the United States; they are all hares. But the early colonists, for some unknown reason, dropped the word hare out of their vocabulary, and it is rarely heard in American speech to this day. When it appears it is almost always applied to the so-called Belgian hare, which, curiously enough, is not a hare at all, but a true rabbit. [Mencken, "The American Language"]
Rabbit punch "chop on the back of the neck" so called from resemblance to a gamekeeper's method of dispatching an injured rabbit. Pulling rabbits from a hat as a conjurer's trick recorded by 1843. Rabbit's foot "good luck charm" first attested 1879, in U.S. Southern black culture. Earlier references are to its use as a tool to apply cosmetic powders.
[N]ear one of them was the dressing-room of the principal danseuse of the establishment, who was at the time of the rising of the curtain consulting a mirror in regard to the effect produced by the application of a rouge-laden rabbit's foot to her cheeks, and whose toilet we must remark, passim, was not entirely completed. ["New York Musical Review and Gazette," Nov. 29, 1856]
Rabbit ears "dipole television antenna" is from 1950. Grose's 1785 "Dictionary of the Vulgar Tongue" has "RABBIT CATCHER. A midwife."
rabble (n.1): c. 1300, "pack of animals," possibly related to Middle English rablen "to gabble, speak in a rapid, confused manner," probably imitative of hurry, noise, and confusion (compare Middle Dutch rabbelen, Low German rabbeln "to chatter"). Meaning "tumultuous crowd of vulgar, noisy people" is from late 14c.; applied contemptuously to the common or low part of any populace from 1550s.
rabble (n.2): iron bar for stirring molten metal, 1864, from French râble, from Old French roable, from Latin rutabulum "rake, fire shovel," from ruere to rake up (perhaps cognate with Lithuanian raju "to pluck out," German roden "to root out").
rabble-rouser (n.): 1842, agent noun from Rabble-rousing, which first attested 1802 in Sydney Smith; from rabble (n.1) + rouse.
Rabelaisian (adj.): 1817, from French author François Rabelais (c. 1490-1553), whose writings "are distinguished by exuberance of imagination and language combined with extravagance and coarseness of humor and satire." [OED]
rabid (adj.): 1610s, "furious, raving," from Latin rabidus "raging, furious, enraged; inspired; ungoverned; rabid," from rabere "be mad, rave" (see rage (v.)). Meaning "made mad by rabies" in English first recorded 1804. Related: Rabidly; rabidness.
rabidity (n.): 1831, from rabid + -ity.
rabies (n.): 1590s, from Latin rabies "madness, rage, fury," related to rabere "be mad, rave" (see rage (v.)). Sense of "extremely fatal infectious disease causing madness in dogs" was a secondary meaning in Latin. Known hydrophobia in humans.
raccoon (n.): also racoon, c. 1600, arocoun, from Algonquian (Powhatan) arahkun, from arahkunem "he scratches with the hands." Early forms included Capt. John Smith's raugroughcum. In Norwegian, vaskebjørn, literally "wash-bear."
race (n.1): "act of running," c. 1300, from Old Norse ras "running, rush (of water)," cognate with Old English ræs "a running, a rush, a leap, jump; a storming, an attack;" or else a survival of the Old English word with spelling influenced by the Old Norse one. The Norse and Old English words are from Proto-Germanic *res- (source also of Middle Dutch rasen "to rave, rage," German rasen, Old English raesettan "to rage" (of fire)), from a variant form of PIE *ers- (1) "be in motion" (see err). Originally a northern word, it became general in English c. 1550. Meaning "act of running" is from early 14c. Meaning "contest of speed" first recorded 1510s.
race (n.2): "people of common descent," a word from the 16th century, from Middle French race, earlier razza "race, breed, lineage, family" (16c.), possibly from Italian razza, of unknown origin (cognate with Spanish and Portuguese raza). Etymologists say no connection with Latin radix "root," though they admit this might have influenced the "tribe, nation" sense.

Original senses in English included "wines with characteristic flavor" (1520), "group of people with common occupation" (c. 1500), and "generation" (1540s). Meaning "tribe, nation, or people regarded as of common stock" is by 1560s. Modern meaning of "one of the great divisions of mankind based on physical peculiarities" is from 1774 (though as OED points out, even among anthropologists there never has been an accepted classification of these).
Just being a Negro doesn't qualify you to understand the race situation any more than being sick makes you an expert on medicine. [Dick Gregory, 1964]
In mid-20c. U.S. music catalogues, "Negro." Klein suggests these derive from Arabic ra's "head, beginning, origin" (compare Hebrew rosh). Old English þeode meant both "race, folk, nation" and "language;" as a verb, geþeodan, it meant "to unite, to join."
race (v.): c. 1200, rasen "to rush," from a Scandinavian source akin to the source of race (n.1), reinforced by the noun in English and by Old English cognate ræsan "to rush headlong, hasten, enter rashly." Meaning "run swiftly" is from 1757. Meaning "run in competition against" is from 1809. Transitive sense of "cause to run" is from 1860. In reference to an engine, etc., "run with uncontrolled speed," from 1862. Related: Raced; racing.
race (n.3): "strong current of water," c. 1300, originally any forward movement or swift running, but especially of water, from Old Norse ras "a rushing" (see race (n.1)). Via Norman French the word entered French as ras, which might have given English race its specialized meaning of "channel of a stream" (especially an artificial one to a mill), which is recorded in English from 1560s.
race-course (n.): 1764, from race (n.1) + course (n.).
race-horse (n.): 1620s, from race (n.1) + horse (n.).
race-riot (n.): 1889, American English, from race (n.2) + riot (n.).
race-track (n.): 1814, from race (n.1) + track (n.).
raceme (n.): type of flower cluster, 1785, from Latin racemus "a cluster of grapes" (see raisin). Related: Racemic; racemism.
racer (n.): 1640s of persons; 1793 of vehicles, agent noun from race (v.).
Rachel: fem. proper name, biblical daughter of Laban and wife of Jacob, from Late Latin, from Greek Rhakhel, from Hebrew Rahel, literally "ewe" (compare Arabic rahil, Aramaic rahla, Akkadian lahru, a metathesized form).
rachio-: also rhachio-, before vowels rachi-, word-forming element meaning "spinal," from Greek rhakhis "spine, ridge, rib of a leaf." Compare Greek rhakhos "thorn hedge."
rachitic (adj.): 1797, from rachitis (1727), medical Latin, from Late Greek rhakhitis (nosos) "rachitic disease, inflammation of the spine," from Greek rhakhis "spine, ridge, rib of a leaf" (see rachio-).
racial (adj.): 1862, from race (n.2) + -ial. Related: Racially.
racialism (n.): "racism," 1879, from racial + -ism. Also see racist.
racialist (n.): 1910, from racial + -ist. Also see racist. As an adjective from 1917.
racialization (n.): 1874, from racial + -ize + -ation.
raciation (n.): "evolutionary development of biological races," 1952, from race (n.2) + ending from speciation, etc.
racing (n.): 1670s, verbal noun from race (v.).
racism (n.): 1936; see racist.
racist: 1932 as a noun, 1938 as an adjective, from race (n.2); racism is first attested 1936 (from French racisme, 1935), originally in the context of Nazi theories. But they replaced earlier words, racialism (1871) and racialist (1917), both often used early 20c. in a British or South African context. In the U.S., race hatred, race prejudice had been used, and, especially in 19c. political contexts, negrophobia.
rack (n.1): "frame with bars," c. 1300, possibly from Middle Dutch rec "framework," literally "something stretched out, related to recken (modern rekken) "stretch out," cognate with Old English reccan "to stretch out," from Proto-Germanic *rak- (source also of Old Saxon rekkian, Old Frisian reza, Old Norse rekja, Old High German recchen, German recken, Gothic uf-rakjan "to stretch out"), from PIE *rog-, from root *reg- "to move in a straight line" (see regal).

Meaning "instrument of torture" first recorded early 15c., perhaps from German rackbank, originally an implement for stretching leather, etc. Mechanical meaning "toothed bar" is from 1797 (see pinion). Meaning "set of antlers" is first attested 1945, American English; hence slang sense of "a woman's breasts" (especially if large), by 1991. Meaning "framework for displaying clothes" is from 1948; hence off the rack (1951) of clothing, as opposed to tailored.
rack (n.2): type of gait of a horse, 1580s, from rack (v.) "move with a fast, lively gait" 1520s in this sense (implied in racking), of unknown origin; perhaps from French racquassure "racking of a horse in his pace," itself of unknown origin. Or perhaps a variant of rock (v.1).
rack (n.3): "clouds driven before the wind," c. 1300, also "rush of wind, collision, crash," originally a northern word, possibly from Old English racu "cloud" (or an unrecorded Scandinavian cognate of it), reinforced by Old Norse rek "wreckage, jetsam," or by influence of Old English wræc "something driven;" from Proto-Germanic *wrakaz, from PIE root *wreg- "to push, shove, drive" (see urge (v.)). Often confused with wrack (n.), especially in phrase rack and ruin (1590s). The distinction is that rack is "driven clouds;" wrack is "seaweed cast up on shore."
rack (v.): "to stretch out for drying," also "to torture on the rack," early 15c., from rack (n.1). Of other pains from 1580s. Figurative sense of "to torment" is from c. 1600. Meaning "raise above a fair level" (of rent, etc.) is from 1550s. Meaning "fit with racks" is from 1580s. Teenager slang meaning "to sleep" is from 1960s (rack (n.) was Navy slang for "bed" in 1940s). Related: Racked; racking. Rack up "register, accumulate, achieve" is first attested 1943 (in "Billboard"), probably from method of keeping score in pool halls.
rack (n.4): "cut of animal meat and bones," 1560s, of unknown origin; perhaps from some resemblance to rack (n.1). Compare rack-bone "vertebrae" (1610s).
racket (n.1): "loud noise," 1560s, perhaps imitative. Klein compares Gaelic racaid "noise." Meaning "dishonest activity" (1785) is perhaps from racquet, via notion of "game," reinforced by rack-rent "extortionate rent" (1590s), from rack (n.1). But it might as well be an extended sense of "loud noise" by way of "noise or disturbance made to distract a pick-pocket's victim."
racket (n.2): "handled paddle or netted bat used in tennis, etc.;" see racquet.
racketeer: 1928 (noun and verb), from racket (n.1) + -eer. Related: Racketeering (1928).
raconteur (n.): "storyteller, person skilled in relating anecdotes," 1828, from French raconteur, from raconter "to recount, tell, narrate," from re- (see re-) + Old French aconter "to count, render account" (see account (v.); and compare recount (v.1)). Related: Raconteuse (fem.).