'appellor' originates from Latin, specifically the word 'appellare', where 'ad-' meant 'to' (or 'toward') and 'pellare' (related to 'pellere') meant 'to drive' or more generally 'to call/address'.

'appellor' changed from Anglo-French/Old French words such as 'apeler'/'apelour' and entered Middle English in forms like 'appellen'/'appellour', eventually becoming the modern English noun 'appellor' (and the related form 'appellant').

Initially it meant 'to call upon or address', but over time it evolved into the legal sense of 'a person who makes an appeal to a higher court'.