Charles Ellicott Commentary Numbers 25:15

"And the name of the Midianitish woman that was slain was Cozbi, the daughter of Zur; he was head of the people of a fathers` house in Midian." — Numbers 25:15 (ASV)

Head over a people, and of a chief house in Midian.— Better, head of the tribes (or, communities) of a father’s house in Midian. Several of the Midianitish tribes, or smaller divisions of a father’s house, may have descended from one tribe-father. In Numbers 31:8, Zur is described as one of the five kings of Midian who were slain by the Israelites.