'assigner' originates from Latin, specifically the word 'assignare', where 'ad-' meant 'to' and 'signare' meant 'to mark'; English formed 'assign' from this Latin root and then derived the noun 'assigner'.

'assign' passed into Middle English from Old French (Old French verb 'assigner') which in turn came from Latin 'assignare'; English formed the agent noun 'assigner' from the verb 'assign'.

Initially it meant 'to mark out or allocate' in the sense of designating or allotting; over time it evolved to include senses such as 'to give someone a task' and legal senses like 'to transfer rights', which inform the modern noun 'assigner'.