'avenger' originates from Middle English, ultimately built from the verb 'avenge' plus the agent suffix '-er'; 'avenge' came from Old French 'avengier' (or 'vengier') meaning 'to take vengeance'.

'avenger' changed from Old French 'avengier' (via Middle English forms such as 'avenge'/'avenger') and eventually became the modern English word 'avenger'.

Initially it meant 'one who takes vengeance', and over time this core meaning has largely remained the same (with additional cultural uses, e.g. as the name of a superhero team).