In Greek mythology, Termerus (Τέρμερος) was a bandit who was killed by Heracles. The episode is referenced in Plutarch's Life of Theseus, in description of Theseus' method of slaying his assailants by returning "the same sort of violence that they offered to him," as Heracles killed Termerus by “breaking his skull in pieces (whence, they say, comes the proverb of 'a Termerian mischief'), for it seems Termerus killed passengers that he met by running with his head against them.”