treacherous (adj.)youdaoicibaDictYouDict[treacherous 词源字典]
early 14c., from Old French trecheros, tricheros "deceitful" (12c.), from trecheor, tricheor "cheat, deceiver, liar, impostor, trickster," agent noun from trechier, trichier "to cheat, trick" (see trick (n.)). Figuratively, of things, from c. 1600. Related: Treacherously; treacherousness. Middle English had treacher "deceiver, cheat, traitor."[treacherous etymology, treacherous origin, 英语词源]