impairyoudaoicibaDictYouDict[impair 词源字典]
impair: [14] If to repair something is to ‘put it right’, it seems logical that to impair something should be to ‘make it wrong’. In fact, though, logic has nothing to do with it, for the two words are quite unrelated. Repair comes ultimately from Latin parāre ‘make ready’, whereas impair goes back via Old French empeirier to Vulgar Latin *impējōrāre ‘make worse’.
[impair etymology, impair origin, 英语词源]
impair (v.)youdaoicibaDictYouDict
late 14c., earlier ampayre, apeyre (c. 1300), from Old French empeirier (Modern French empirer), from Vulgar Latin *impeiorare "make worse," from assimilated form of in- "into, in" (see in- (2)) + Late Latin peiorare "make worse" (see pejorative). In reference to driving under the influence of alcohol, first recorded 1951 in Canadian English. Related: Impaired; impairing.