'annexure' originates from Latin, specifically the word 'annexus', where 'ad-' (often assimilated to 'an-') meant 'to' and 'nectere' meant 'to bind' or 'tie'.

'annexure' changed through Late Latin and Old French forms: from Latin 'annexus' to Old French/Medieval Latin forms such as 'annexer'/'annexura', and eventually became the modern English word 'annexure'.

Initially, it meant 'something joined or attached', and over time it evolved into the current senses of 'an attached document (appendix)' and 'an attached building (annex)'.