'annexer' originates from Latin, specifically the word 'annexus' (the past participle of 'annectere'), where the prefix 'ad-' (assimilated to 'an-') meant 'to' and 'nectere' meant 'to bind or tie'.

'annexer' entered English via Old French 'annexer' (verb) and Middle English forms; the Latin verb and participial forms gave rise to the French and then English verb 'annex', and the agent noun formation produced 'annexer' in later English usage.

Initially it meant 'to bind or attach', but over time it evolved into the modern sense of 'to add, incorporate, or take (especially territory) into a larger entity'.