The name of the Midianite woman who was killed was Cozbi daughter of Zur. He was a leader over the people of a clan of Midian.

because they bring trouble to you by their treachery with which they have deceived you in the matter of Peor, and in the matter of Cozbi, the daughter of a prince of Midian, their sister, who was killed on the day of the plague that happened as a result of Peor.”