troopyoudaoicibaDictYouDict[troop 词源字典]
troop: [16] Troop was borrowed from French troupe (acquired again as troupe in the 19th century). This appears to have been a backformation from troupeau ‘flock, herd’, a diminutive formation based on Latin troppus. And troppus itself may have been of Germanic origin. By the time the word reached English it was already being applied to a ‘group of soldiers’, and its plural was being used as a collective term for ‘soldiers’.
=> troupe[troop etymology, troop origin, 英语词源]
troop (n.)youdaoicibaDictYouDict
1540s, "body of soldiers," 1540s, from Middle French troupe, from Old French trope "band of people, company, troop, crowd" (13c.), of uncertain origin, perhaps from Frankish *throp "assembly, gathering of people" or another Germanic source, perhaps related to Old English ðorp, Old Norse thorp "village" (see thorp). OED derives the French word from Latin troppus "flock," which is of unknown origin but also might be from the proposed Germanic source. Of groups of animals from 1580s. Specifically as "a subdivision of a cavalry force" from 1580s; of Boy Scouts from 1908. Troops "armed forces" is from 1590s.
troop (v.)youdaoicibaDictYouDict
1560s, "to assemble," from troop (n.). Meaning "to march" is recorded from 1590s; that of "to go in great numbers, to flock" is from c. 1600. Related: Trooped; trooping.