'bellicist' originates from Latin, specifically the word 'bellum', where the root 'bell-' meant 'war' and the agentive suffix '-ist' (via Greek/Latin suffixes) meant 'one who...'.

'bellicist' changed from the adjective 'bellicose' (from Latin 'bellicosus', itself from 'bellum') combined with the agentive suffix '-ist' and eventually became the modern English noun 'bellicist'.

Initially, it meant 'warlike' (as in the adjective 'bellicose'), but over time it evolved into its current meaning of 'a person who advocates war' (a proponent of military action).