Nefarious

google

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early 17th century: from Latin nefarius, from nefas, nefar- ‘wrong’ (from ne- ‘not’ + fas ‘divine law’) + -ous.

wiktionary

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From Latin nefārius(“execrable, abominable”), from nefās(“something contrary to divine law, an impious deed, sin, crime”), from ne-(“not”) + fās(“the dictates of religion, divine law”), which is related to Latin for(“I speak, I say”) and cognate to Ancient Greek φημί(phēmí, “I say”).

etymonline

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nefarious (adj.)

"wicked in the extreme," c. 1600, from Latin nefarius "wicked, abominable, impious," from nefas "crime, wrong, impiety," from ne- "not" (from PIE root *ne- "not") + fas "right, lawful, divinely spoken," related to fari "to speak," from PIE root *bha- (2) "to speak, tell, say." Related: Nefariously; nefariousness.