irresponsible (adj.)youdaoicibaDictYouDict[irresponsible 词源字典]
1640s, "not legally answerable for conduct or actions," from assimilated form of in- (1) "not, opposite of" + responsible. Meaning "not acting with a sense of responsibility" is from 1680s. Related: Irresponsibly.[irresponsible etymology, irresponsible origin, 英语词源]