devil's advocate (n.)youdaoicibaDictYouDict[devil's advocate 词源字典]
1760, translating Latin advocatus diaboli, one whose job it is to urge against the canonization of a candidate for sainthood. "[F]ar from being the whitewasher of the wicked, the [devil's advocate] is the blackener of the good." [Fowler][devil's advocate etymology, devil's advocate origin, 英语词源]