Joel means Lord is God
and Abijah means my father is the Lord.
Exactly why we are told their names is not clear seeing as they will not be mentioned again in the Bible narrative. Beersheba, located on the southern borders of Israel, was likely an important religious and judicial site at this time (see Amos 5:5).1 Presumably it is mentioned to absolve Samuel of any complicity in their injustice,2 seeing as there was a significant distance between Ramah and Beersheba.
2 The name of his firstborn son was Joel, and the name of his second, Abijah; they were judges in Beersheba.