irresistible (adj.)youdaoicibaDictYouDict[irresistible 词源字典]
1590s, from Late Latin irresistibilis, from assimilated form of in- "not, opposite of" (see in- (1)) + resistere (see resist). Related: Irresistibly; irresistibility. [irresistible etymology, irresistible origin, 英语词源]