This is a bit of an aside, but something I've always wondered is: why does this branch of mathematics get labeled as Queueing "theory"?

From my brief understanding, when someone talks about Queueing theory they are not talking about a singular "theory" but they mean something much broader. It doesn't seem as if there is something here that needs to be proved or disproved.

This is a part of naming in mathematics that has always perplexed me.

edit: not sure why this would get downvoted, seems like a simple neophyte question