nefariousyoudaoicibaDictYouDict
nefarious: [16] Latin nefās ‘sin’ denoted etymologically something that was contrary to the divine law. It was a compound noun formed from the negative particle ne- and fās ‘divine law, dictates of religion’. From it was derived the adjective nefārius, source of English nefarious.
nefarious (adj.)youdaoicibaDictYouDict
c. 1600, from Latin nefarius "wicked, abominable, impious," from nefas "crime, wrong, impiety," from ne- "not" (see un-) + fas "right, lawful, divinely spoken," related to fari "to speak," from PIE root *bha- (2) "to speak, tell, say" (see fame (n.)). Related: Nefariously.