Jerome Chanes writes:
What—or who—in the Bible is b'liya'al? In biblical Hebrew, ben-b'liya'al, a “son of b'liya'al,” is the ultimate pejorative by which someone can be called. In Christian literature, Belial is Satan's helper or even Satan himself, and in today's popular culture he is a kind of evil Grand Poobah who turns up in films and computer games. What do you make of it—or of him?
In the Hebrew Bible, where it occurs 27 times, b'liya'al is indeed a puzzling word, one with no obvious etymology. Most often it occurs, as Mr. Chanes observes, in the expression ben or b'ney b'liya'al, son or sons of b'liya'al. (There is one case, too, of bat b'liya'al, a daughter of b'liya'al.) But one also finds the term ish (or adam) b'liya'al, a man of b'liya'al, and even, in the book of Psalms, na?aley b'liya'al, torrents or floodwaters of b'liya'al.