be-el'-ze-bub (in the King James Version and the Revised Version (British and American) is an error (after the Vulgate) for Beelzebul (Revised Version margin) Beelzeboul; Westcott and Hort, The New Testament in Greek, Beezeboul):
In the time of Christ this was the current name for the chief or prince of demons, and was identified with
SATAN (which see) and the DEVIL (which see). The Jews committed the unpardonable sin of ascribing Christ's work of casting out demons to Beelzebul, thus ascribing to the worst source the supreme manifestation of goodness (Matthew 10:25; 12:24,27; Mark 3:22; Luke 11:15,18,19). There can be little doubt that it is the same name as BAALZEBUB (which see). It is a well-known phenomenon in the history of religions that the gods of one nation become the devils of its neighbors and enemies. When the Aryans divided into Indians and Iranians, the Devas remained gods for the Indians, but became devils (daevas) for the Iranians, while the Ahuras remained gods for the Iranians and became devils (asuras) for the Indians. Why Baalzebub became Beelzebul, why the b changed into l, is a matter of conjecture. It may have been an accident of popular pronunciation, or a conscious perversion (Beelzebul in Syriac = "lord of dung"), or Old Testament zebhubh may have been a perversion, accidental or intentional of zebhul (= "house"), so that Baalzebul meant "lord of the house." These are the chief theories offered (Cheyne in EB; Barton in Hastings, ERE).