Why did Saul name two of his sons Eshbaal and Merib-baal?

A common practice in ancient Israel was to incorporate god's name when naming a son. Two of Saul's sons have interesting names: Merib-baal and Eshbaal (A later redactor changed the names to Mephiboshet and Ishboshet to hide the fact that their names contain the word baal.) That being said, what motivated Saul, a worshiper of Yahweh, to incorporate Baal into his sons' names? Why did Saul's sons' name do not contain "yah", instead of "baal"?