Zephaniah 1:4 (ESV)

4 “I will stretch out my hand against Judah and against all the inhabitants of Jerusalem; and I will cut off from this place the remnant of Baal and the name of the idolatrous priests along with the priests,

Baal could be read as a simple common name meaning master (Isaiah 1:3), ruler (Isaiah 16:8), or husband (Deuteronomy 24:4). Baal was the god of fertility and storm: his function in Canaanite religion was to make land, animals, and humans fertile. Baal was also the god of “sexual free-for-all (Numbers 25:1–3). Human sexual acts were publicly offered to him to prompt him to perform his work of fertilization."1

When Israel entered Canaan, the Canaanites remained in the land. The people of Israel learned to farm and to worship Baal from the Canaanites. The Canaanites believed that the Baals ensured the fertility of the land. For this reason, God had commanded Israel to exterminate the Canaanites from the land (Deuteronomy 7:1–26). Israel’s failure to do so is what led to centuries of God’s people worshipped the Lord while also giving allegiance to the Baal gods.