“Hadad” means mighty

Hadad: originally the indigenous appellation of the sun among the Syrians, and thence transferred to the king as the highest of earthly authorities. The title appears to have been an official one, like Pharaoh. It is found occasionally in the altered form Hadar. (Genesis 25:15; 36:39) compared with 1Chr 1:30,50

1. Son of Ishmael. (Genesis 25:15; 1 Chronicles 1:30)
2. A king of Edom who gained an important victory over the Midianites on the field of Moab. (Genesis 36:35; 1 Chronicles 1:46)
3. Also a king of Edom, with Pau for his capital. (1 Chronicles 1:50)
4. A member of the royal house Or Edom. (1 Kings 11:14) ff. In his childhood he escaped the massacre under Joab, and fled with a band of followers into Egypt. Pharaoh, the predecessor of Solomon's father-in-law, treated him kindly, and gave him his sister-in-law in marriage. After David's death Hadad resolved to attempt the recovery of his dominion. He left Egypt and returned to his own country.