raciation (n.)youdaoicibaDictYouDict[raciation 词源字典]
"evolutionary development of biological races," 1952, from race (n.2) + ending from speciation, etc.[raciation etymology, raciation origin, 英语词源]
racing (n.)youdaoicibaDictYouDict
1670s, verbal noun from race (v.).
racism (n.)youdaoicibaDictYouDict
1936; see racist.
racistyoudaoicibaDictYouDict
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)youdaoicibaDictYouDict
"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- (cognates: 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)youdaoicibaDictYouDict
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)youdaoicibaDictYouDict
"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.)youdaoicibaDictYouDict
"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)youdaoicibaDictYouDict
"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)youdaoicibaDictYouDict
"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)youdaoicibaDictYouDict
"handled paddle or netted bat used in tennis, etc.;" see racquet.
racketeeryoudaoicibaDictYouDict
1928 (noun and verb), from racket (n.1) + -eer. Related: Racketeering (1928).
raconteur (n.)youdaoicibaDictYouDict
"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.).
racquet (n.)youdaoicibaDictYouDict
"handled hitting device used in tennis, etc.," c. 1500, probably originally "tennis-like game played with open hand" (late 14c.), from Middle French rachette, requette (Modern French raquette) "racket for hitting; palm of the hand," perhaps via Italian racchetta or Spanish raqueta, both often said to be from Arabic rahat, a form of raha "palm of the hand," but this has been doubted. Compare French jeu de paume "tennis," literally "play with the palm of the hand," and compare tennis).
racquetball (n.)youdaoicibaDictYouDict
1972, from racquet + ball (n.1).
racy (adj.)youdaoicibaDictYouDict
1650s, "having a characteristic taste" (of wines, fruits, etc.), from race (n.2) in its older sense of "flavor" or in the sense "class of wines" + -y (2); meaning "having a quality of vigor" (1660s) led to that of "improper, risqué," first recorded 1901, probably reinforced by phrase racy of the soil "earthy" (1870). Related: Racily; raciness.
radyoudaoicibaDictYouDict
"x-ray dose unit," 1918, shortened form of radiation (q.v.). As shortened form of radical (n.), it is attested in political slang from 1820. Teen slang sense of "extraordinary, wonderful" is from late 1970s (see radical (adj.)).
radar (n.)youdaoicibaDictYouDict
"electronic system for locating objects by means of radio waves," 1941, acronym (more or less) from radio detecting and ranging. The U.S. choice, it won out over British radiolocation. Figurative from 1950.
radial (adj.)youdaoicibaDictYouDict
c. 1400, "of or like a ray or radius," from Medieval Latin radialis, from Latin radius "shaft, rod; spoke of a wheel; beam of light" (see radius). As a noun, a type of tire, attested from 1965, short for radial-ply (tire). Related: Radially.
radian (n.)youdaoicibaDictYouDict
"angle subtended at the center of a circle by an arc equal in length to the radius," 1879, from radius.