'bellicist' originates from Latin, specifically the word 'bellum', where 'bellum' meant 'war'. The English form is built from the combining element 'bellic-' (from Latin 'bellicus') plus the agent suffix '-ist'.

'bellum' in Latin gave rise to Late Latin 'bellicus' (meaning 'warlike'), which contributed to words like Middle English/Old French 'bellicose' (from Latin 'bellicosus'); English later formed the agent noun 'bellicist' by adding '-ist' to the bellic- element.

Originally associated with being 'warlike' or 'pertaining to war', the sense shifted to denote a person who advocates or favors war or aggressive policies.