See how you translated similar words in [1 Samuel 3:3](../03/03.md). This is the a same as the "ark of the covenant of Yahweh" in [1 Samuel 4:3](../04/03.md).
Possible meanings are 1) they were speaking the proper name of the God of Israel or 2) they believed that Israel worshiped one of many gods, "the god of Israel." See how you translated this in [1 Samuel 5:7](../05/07.md).