'avengeful' originates from English, specifically formed from the verb 'avenge' + the suffix '-ful'. 'Avenge' itself comes from Old French 'avengier', where the element meant 'to take vengeance'.

'avengeful' developed by adding the productive English adjectival suffix '-ful' to Middle/Old English forms of 'avenge' (from Old French 'avengier'), producing the modern adjective 'avengeful'.

Initially the root meant 'to take vengeance' and over time the derived adjective came to mean 'characterized by a tendency to take vengeance' (i.e., 'vengeful').