More about agonist
The English noun agonist comes from the rare Late Latin noun agōnista, “an athlete or combatant for a prize in the games,” a word used once by St. Augustine in a sermon. Latin agōnista betrays its Greek origin with its –ista agent suffix (borrowed from Greek -istḗs). In Greek, agōnistḗs means “a combatant, contestant (in athletic games), a champion, a pleader or public speaker,” which covers a lot of territory when you consider the roles that competitive athletic games and public speaking (including criminal and civil trials) occupied in ancient Greek life. Agōnistḗs is a derivative of the noun agōnía, one of whose many meanings is “mental or spiritual anguish, agony,” which influenced one of the English meanings of agonist but doesn’t occur in Greek agōnistḗs. Agonist entered English in the first half of the 17th century.