'annexor' originates from Latin, specifically from the past participle 'annexus' (from the verb 'annectere'), where the prefix 'ad-' meant 'to' and 'nectere' meant 'to bind or tie'.

'annexor' passed into English via Old French/Medieval Latin forms (e.g. Old French 'annexer'/'annexer' and Medieval Latin agents with suffix '-or'), evolving into the modern English agent noun 'annexor'.

Initially related to being 'joined' or 'attached' (the sense of 'bound to'), over time it came to mean specifically 'one who annexes'—a person or state that incorporates territory or property.