Sheol (שְׁאוֹל) is a place mentioned in the Tanakh as the destination of the dead. Shaul (שָׁאוּל) is the Hebrew name for Saul, the first Israelite king, as well as Paul the Apostle. Messianic congregations frequently use “Shaul” in place of “Paul” to make the New Testament seem more Jewish.
Note that the consonants for both words are the same in Hebrew. As you can imagine, this poses problems for Messianic congregations whose leaders can’t actually read Hebrew—for example, Yeshuat Yisrael, which put together this slide for one of the many PowerPoint sermons it offers on its website.