rotate (v.)youdaoicibaDictYouDict[rotate 词源字典]
1794, intransitive, back-formation from rotation. Transitive sense from 1823. Related: Rotated; rotating. Rotator "muscle which allows a part to be moved circularly" is recorded from 1670s.[rotate etymology, rotate origin, 英语词源]
rotor (n.)youdaoicibaDictYouDict
1873, irregular shortening of rotator (see rotate (v.)), originally in mathematics. Mechanical sense is attested from 1903; specifically of helicopters from 1930.
racemic acidyoudaoicibaDictYouDict
"A compound (originally obtained from the tartar in grape juice) consisting of equal proportions of the laevo- and dextrorotatory isomers of tartaric acid. Now chiefly historical", Mid 19th cent.; earliest use found in Records of General Science.
racemicyoudaoicibaDictYouDict
"Composed of dextrorotatory and laevorotatory forms of a compound in equal proportion", Early 19th century (in racemic acid): from French racémique 'derived from grape juice' (originally referring to tartaric acid in this) + -ic.