'argumentator' originates from Latin, specifically the Late Latin word 'argumentator', where 'argumentum' meant 'proof, evidence' (from Latin 'arguere' meaning 'to make clear, prove, accuse') and the suffix '-ator' was an agent-forming suffix meaning 'one who'.

'argumentator' appears in Medieval and Early Modern Latin and occasionally in English texts as a learned or formal term meaning 'one who argues or proves'; it passed into English usage by way of learned borrowing and rare use in legal, rhetorical, or scholarly contexts.

Initially, it meant 'one who provides proof or demonstrates (a case)'; over time it broadened (in rare uses) to mean more generally 'one who argues' or 'a debater'.