Here’s my latest comic: https://inhumaneresourcescomic.com/#/panel/783.
So the name is a stupid reference to the BFG9000 from the Doom fanchise. In Doom, it’s a tongue-in-cheek reference to Big Fucking Gun. The implication is that some of the engineers who worked on the BFG were Doom fans and named the gun after it.
The Bilateral Field Gauss projector is basically a small railgun.