Head over a people, and of a chief house in Midian. Rather, "head of tribes ( אֻמּוֹת, for the use of which cf. Genesis 25:16) of a father's house in Midian." It seems to mean that several clans descended from one tribe-father looked up to Zur as their head.
In Numbers 31:8 he is called one of the five "kings" of Midian. That the daughter of such a man should have been selected, and should have been willing, to play such a part throws a strong light upon the studied character and the peculiar danger of the seduction.