'arch-villain' is formed from the prefix 'arch-' (from Greek 'arkhos') meaning 'chief, principal', combined with 'villain' (from Old French 'vilain', from Latin 'villanus') meaning 'person of the villa (farmhand)'.

'villain' changed from Latin 'villanus' to Old French 'vilain' and entered Middle English as 'villain' originally meaning 'farmhand' or 'rustic', then later 'low-born or base person' and finally 'wicked person'. The prefix 'arch-' comes from Greek 'arkhos' via Latin/Old French usage to form compounds meaning 'principal' or 'chief', producing the compound 'arch-villain' to denote the chief wicked antagonist.

Initially, 'villain' meant 'farmhand or someone associated with a villa'; over time it shifted to mean 'base or low-born person' and then 'wicked person' or 'antagonist'. 'Arch-' retained the meaning 'chief', so 'arch-villain' evolved to mean the principal evil antagonist.