Probably from shachar; black; Ashchur, an Israelite -- Ashur.
see HEBREW shachar
H806. Ashchuwr
אַשְׁחוּר proper name, masculine in Judah, called תְקוֺעַ ׳א אֲבִי 1 Chronicles 2:24; 4:5; Ασχω, Σαρα; A Ασδωδ, Ασχουρ; ᵐ5L Ασσωρ, Ασοωρ.
II. שׁחר (√ of following; MI15 שחרת, Arabic , Assyrian šêru, Late Hebrew שַׁחַר, Aramaic שַׁחֲרָא all dawn).