Judo was a form of martial art which was originally developed in Japan on Earth by Kano Jigoro. The defense combatant uses the blows and momentum of the attacker against them; thereby weakening the threat, with as little brute force and energy possible. (TNG novel: The Romulan Prize)
James T. Kirk's error is completely understandable. After World War II, United States military training referred to all forms of unarmed, Eastern inspired combat as "Judo". In 1968 anyone who didn't know what they were talking (or writing) about could easily make this mistake.