'assuror' originates from French, specifically the word 'assureur', where 'assurer' meant 'to make safe, to assure' (from Latin roots related to 'securus' meaning 'secure').

'assuror' changed from Middle English/Anglo-French forms such as 'assurour' influenced by Old French 'asseurer' and the French agent noun 'assureur', and eventually appeared in modern English as 'assuror'.

Initially it meant 'one who makes safe or gives assurance'; over time it retained that core sense and came to be used specifically of those who provide insurance or formal guarantees.