Baal of Peor might refer to Chemosh by another name (21:29). More likely, it refers to Baal, which means “lord.” Baal was a Canaanite god. The Moabites honored several gods, and Baal was probably one of them.
Many place names include the name Baal, such as Baal-gad, Baal-hermon, Baal-meon, and Baal-peor. These names likely marked local shrines where people worshiped Baal in different forms.
Peor was a mountain from which Balaam could see the camp of Israel in the plains of Moab. Nearby was a shrine called Beth-peor (23:28; 25:3, 5, 18; 31:16; Deuteronomy 3:29; 4:3, 46; 34:6; Joshua 13:20; 22:17).
Israel’s worship of false gods made the Lord very angry. As a result, a plague broke out among the people (Numbers 25:8–9; 26:1; compare 11:1, 10; 12:9).