The name "Beelzebub" (a corruption of "Baalzebub") is actually a pun on the name of the Canaanite god Baalzebul (Often shortened to just Baal). Baalzebul means "lord of lords." "Baalzebub" means "lord of the flies." Not very respectful, and taken in context it hardly summons the terror that eventually grew up around that name. It was intended to trivialize his power, but instead I think the imagery of "Lord of the Flies" (which is pretty scary and gross if you think about it) was responsible for the name's longevity. (I mean, jeesh, everyone calls their god "lord of lords.")