The word Beelzebub means ' The god of flies ' in Hebrew. He was worshiped at Ekron , a city of the Philistines as a fertility god. Beelzebub is called is Matthew, xii, 24, 'The prince of the devils’; hence he is represented by Milton as next to Satan in power and in crime. The crime is the crime of rebellion against god. Beelzebub followed Satan, next in the act of rebellion. Next to Satan, Beelzebub shared the greatest responsibility for the rebellion against god and overthrow of the angels.
Satan proposes to summon his followers who are still confounded that they may either share misery with him in Hell or prepare for another contest with god. In reply to this, Beelzebub highly praises Satan as their leader: 'Leader of those armies bright, / Which but th' omnipotent none could have foil’d. In his second speech [lines 271 -282 ] , Beelzebub assures Satan of the fallen angels ' undying allegiance and devotion to Satan . In their with gods host, they had been cheered up by Satan’s voice. This time also they will rise from their stupefied condition on the lake of fire at their leader's call. To quote from Prof. Raleigh's Milton, ' His followers are devotedly attached to him: they admire him that for the general safety he [Satan] despised his own.’
Ref: 1. A. R. Waller: The Writings of John Milton
2. H. R. Mead: Biography of John Milton