Hadad = "mighty"

 1) son of Ishmael
 2) a king of Edom who gained an important victory over the Midianites
    on the field of Moab
 3) another king of Edom, with Pau for his capital
 4) a member of the royal house of Edom who escaped the massacre under
    Joab and fled with a band of followers into Egypt; after David's
    death, he returned to his own country