'annexion' originates from Medieval Latin, specifically the word 'annexio', where 'ad-' (or assimilated as 'an-') meant 'to' and 'nectere' meant 'to bind or tie'.

'annexion' changed from the Medieval Latin word 'annexio' and passed into Old French as 'annexion', and eventually entered English as the word 'annexion'.

Initially, it meant 'a joining or attaching', but over time it evolved into its current usage often meaning 'the act of adding territory' (annexation).