"stirrup bone in the middle ear," 1660s, from Modern Latin (1560s), special use of Medieval Latin stapes "stirrup," probably an alteration of Late Latin stapia, related to stare "to stand" + pedem, accusative of pes "foot" (see foot). So called because the bone is shaped like a stirrup. This was an invented Medieval Latin word for "stirrup," for which there was no classical Latin word, as the ancients did not use stirrups.