The word "助纣为虐" is formed by combining four characters: "助" meaning "to help", "纣" referring to the tyrannical King Zhou of the Shang Dynasty, "为" meaning "to do", and "虐" meaning "cruelty". It literally translates to "helping Zhou commit tyranny", creating an idiom that metaphorically denotes aiding a villain in evil deeds, based on the historical notoriety of King Zhou.