It's from a meme, "Money printer go brrrr" ~~which was I think a spin off of the "It prints money!" meme for the original Wii~~ (Edit: did some research and I think they're unrelated.) Its the sound of the machine, printing money, it go brrr.

I've seen it used for all kinds of things, but "go brrr" is basically a dismissive way of talking about how "winning" something is.

Edit: I think Picard Manuever explains it better actually, and while I don't think my usage note is untrue from how I've seen the meme used in evolutions, I'd have to agree that it originally and usually takes the form they described.