A myrmidon is someone who will do whatever you say. A schoolyard bully often has a myrmidon for a best friend — someone who is sure to never point out that it's wrong to hassle other kids.
To pronounce myrmidon correctly, say "MUR-muh-don." A celebrity who hates it when people challenge her ideas probably has only myrmidons for friends. A myrmidon can also be specifically someone who unquestioningly carries out the violent orders of a boss. The word originated with the Greek Myrmidones, the followers of Achilles during the Trojan War, who were said to have been transformed into men from ants, which in Greek is myrmex.