audacious (adj.)youdaoicibaDictYouDict[audacious 词源字典]
1540s, "confident, intrepid," from Middle French audacieux, from audace "boldness," from Latin audacia "daring, boldness, courage," from audax "brave, bold, daring," but more often "bold" in a bad sense, "audacious, rash, foolhardy," from audere "to dare, be bold." Bad sense of "shameless" is attested from 1590s in English. Related: Audaciously.[audacious etymology, audacious origin, 英语词源]