(1) (chadhadh, "sharpness"): One of the twelve sons of Ishmael (Ge 25:15, where the King James Version, following a mistake in Hebrew text, has "Hadar"; but "Hadad" is found in parallel passage 1Ch 1:30; the Revised Version (British and American) reads "Hadad" in both places).
(2) (hadhadh): A king of Edom, son of Bedad (Ge 36:35-36 parallel 1Ch 1:46-47), "who smote Midian in the field of Moab," and whose "city was Avith."
(3) Another king of Edom, written "Hadar" in Ge 36:39 by a copyist's mistake, but "Hadad" in the parallel passage 1Ch 1:50-51. His city was Pau or Palestine.
(4) A member of the royal family of Edom in David's time, who as a child escaped Joab's slaughter of the Edomites, and fled to Egypt. On David's death he returned to Edom, where he made trouble for Solomon by stirring up the Edomites against the rule of Israel (1Ki 11:14-22,25).
(5) The supreme god of Syria, whose name is found in Scripture in the names of Syrian kings, Benhadad, Hadadezer. The god Hadad (= perhaps, "maker of loud noise") is mentioned in Assyrian inscriptions, and called on the monolith of Shalmaneser "the god of Aleppo." In the Assyrian inscriptions he is identified with the air-god Rammon or Rimmon. The union of the two names in Zec 12:11 suggests this identity, though the reference is uncertain, some regarding Hadadrimmon as the name of a place, others as the name of the god--"Hadad (is) Rimmon." The name "Hadad" is found in various other forms: Adad, Dadu, and Dadda. See A. H. Sayce in HDB under the word "Hadad."
George Rice Hovey