Real Dictionary

Damon and Pythias in British English
friends so devoted to each other that when Pythias, who has been condemned to death, wants time to arrange his affairs, Damon pledges his life that his friend will return: Pythias returns and both are pardoned
noun: two friends noted for their mutual loyalty. Damon offered himself as a hostage for Pythias, who was to be executed for treason by Dionysius of Syracuse. When Pythias returned to save his friend's life, he was pardoned
noun: two friends whose mutual loyalty was shown by Damon's offer of his life as pledge that Pythias would return from settling his affairs to be executed for rebelling against Dionysius: Pythias returned, and Dionysius relented and pardoned them both