'exiler' is formed in English by adding the agent suffix '-er' to the verb 'exile', which itself originates from Latin 'exsilium' or 'exilium' meaning 'banishment'.

'exiler' was formed from Middle English 'exilen'/'exile' (verb and noun taken from Old French 'exil' or 'esil') which in turn came from Latin 'exsilium'/'exilium'; the modern English noun 'exiler' follows the regular agent-noun formation with '-er'.

Initially Latin 'exsilium' referred to the state or act of banishment; in English 'exile' came to mean both the state and the act, and 'exiler' specifically denotes the agent who banishes (or, rarely, one who is banished in nonstandard use).