'appellant' originates from Latin, specifically the word 'appellare' (via Old French/Anglo-French), where the prefix 'ad-' (assimilated to 'ap-') meant 'to/toward' and the root related to calling/addressing (from 'appellare' meaning 'to call upon').

'appellant' developed from the Old French/Anglo-French verb (Old French 'apeler' / Anglo-French forms) and the Medieval Latin participial forms of 'appellare'; it entered Middle English in forms like 'appellen' and later produced the agent noun 'appellant' (literally 'one who appeals').

Initially, the Latin verb meant 'to call or address'; over time the sense specialized in legal contexts to mean 'to make an appeal' and the noun came to mean 'one who appeals a court decision.'