faultless (adj.)youdaoicibaDictYouDict[faultless 词源字典]
mid-14c., "having no blemishes or imperfections," from fault (n.) + -less. Meaning "having no blame, culpability, or guilt" is from 1570s. Related: Faultlessly; faultlessness.[faultless etymology, faultless origin, 英语词源]