We're not told for sure where Bolg had his seat, but Mount Gundabad is recorded as the capital of the northern Orcs, and as their leader it seems reasonable to guess that Bolg ruled his people from that mountain. His father Azog, however, seems to have been associated with Moria, so there is a possibility that Bolg also ruled from there.

Most of Tolkien's Orc-names are simply meaningless, but there is a slight possibility that Bolg's name derives from Old English. The word gebolgen in that language comes from the verb 'to be made angry', and indeed that exactly describes Bolg's role in the story of the The Hobbit.

In an early name-list appearing in volume IV of The History of Middle-earth, Bolgen is given as an Old English name for Melkor, using the same verbal root. It's clear, therefore, that Tolkien had already considered this as a name for an evil being, so there's at least a possibility that Bolg inherited his name from this source.

Another possibility is that the name comes from an early example of Tolkien's invented languages, known as Mágol or Old Mágo. That language was by no means as developed as the better known Elvish tongues, but at one time Tolkien considered using it as the Orkish language, and in that tongue the word bolg meant 'strong'.