'atavistic' originates from English, ultimately derived from the French word 'atavisme' and ultimately from the Latin word 'atavus', where 'atavus' meant 'ancestor' or 'great-grandfather'.

'atavus' changed to Late Latin 'atavismus', then to French 'atavisme', which entered English as 'atavism' and later formed the adjective 'atavistic'.

Initially it meant 'descent from or resemblance to an ancestor', but over time it evolved to its current sense of 'reversion to primitive or ancestral traits'.