complacent (adj.)youdaoicibaDictYouDict[complacent 词源字典]
1650s, "pleasing," from Latin complacentem (nominative complacens) "pleasing," present participle of complacere "be very pleasing" (see complacence). Meaning "pleased with oneself" is from 1767. Related: Complacently.[complacent etymology, complacent origin, 英语词源]
self-complacent (adj.)youdaoicibaDictYouDict
1760, back-formation from self-complacency or else from self- + complacent. Related: Self-complacently.