'banisher' originates from English, formed by adding the agentive suffix '-er' to the verb 'banish', where 'banish' comes from Old French 'banir', meaning 'to proclaim, banish'.

'banish' changed from Old French word 'banir' and eventually became the modern English word 'banish', with 'banisher' formed later as a noun.

Initially, 'banish' meant 'to proclaim or order someone away', but over time it evolved into its current meaning of 'to force someone to leave a place'. 'Banisher' thus means 'one who banishes'.