'annexive' originates from Latin, specifically the word 'annexus', where the prefix/root 'ad-' (appearing as 'an-') meant 'to' and 'nectere' meant 'to bind or tie'.

'annexive' developed from Latin 'annexus' (past participle of 'annectere'), passed into Medieval/Old French as forms such as 'annexer' and into Middle English as 'annex', and later English formed the adjectival back-formation 'annexive'.

Initially it conveyed the idea 'tied to' or 'joined', and over time the sense shifted toward 'added or attached (often territorially)'; the modern adjectival use describes something relating to annexation or attachment.