Hadad is mentioned 3 times in scripture, across 2 books of the Old Testament. First named in scripture around 1853 BC.
One of the Edomitish kings (Gen. 36:39) about the time of Saul. Called also Hadad (1 Chr. 1:50, 51).
It is probable that in these cases Hadar may be an error simply of transcription for Hadad.