In Irish mythology, Ferdiad (also Fer Diad, Ferdia) was Cuchulainn's best friend and foster-brother. He trained with him for years in Scotland under the famed She-Warrior Scathach. He was persuaded to fight against Cuchulainn by Queen Medb in the Tain Bo Cuailgne . After three days of battle at a river ford, Ferdiad died in the battle when Cuchulainn used his magical spear the Gae Bulg, which once thrown could not be stopped.
