'appointee' originates from the verb 'appoint' plus the French-derived suffix '-ee' (used to indicate a person who receives an action). 'Appoint' itself comes from Old French 'apointer' (to arrange or fix).

'Appoint' came into Middle English from Old French 'apointer'; English later formed 'appointee' by adding the suffix '-ee' (from French) to mean 'one who is appointed'.

Initially formed to mean 'one who has been appointed,' and it has retained that basic meaning into modern English.