'atavist' originates from Latin, specifically the word 'atavus', where 'atavus' meant 'ancestor' or 'forefather'.

'atavist' developed from the noun 'atavism' (from Modern Latin 'atavismus'), a 19th-century scientific term for the reappearance of ancestral traits; English adopted 'atavism' and later formed the agent noun 'atavist' to denote a person exhibiting such reversion.

Initially, the Latin root 'atavus' simply meant 'ancestor' or 'forefather', but over time it evolved into the biological sense of 'reappearance of ancestral traits' and then into the modern sense of 'a person showing such traits'.