apropos (adv.)youdaoicibaDictYouDict[apropos 词源字典]
1660s, "opportunely," from French à propos "to the purpose," from propos "thing said in conversation, talk; purpose, plan," from Latin propositium "purpose," past participle of proponere "to set forth, propose" (see propound). Meaning "as regards" is 1761, from French. As an adjective, "to the point or purpose," from 1690s.[apropos etymology, apropos origin, 英语词源]