'militant' originates from Latin, specifically the word 'militare', where the root 'milit-' related to 'soldier' or 'to serve as a soldier'.

'militant' changed from the Late Latin present participle 'militans' into Old French and Middle English forms and eventually became the modern English word 'militant'.

Initially it meant 'serving as a soldier' or 'warlike', but over time it evolved into the current meaning of 'combative or aggressively active in support of a cause'.