Short for “Ratskeller,” which is German for “dingy but reknowned punk club in Boston where the Dropkick Murphys and the Mighty Mighty Bosstones had their first gigs.” Oh, wait. I’m sorry. It actually means the cellar under the “Rathaus,” or City Hall, where there was often a restaurant or bar. So it’s triply appropriate: 1) it’s in the cellar of 2) Lyons Hall, which is kind of BC’s city hall in 3) Boston, where the punk club of the same name was nicknamed “The Rat,” because, well, maybe there were some. en.wikipedia.org/wiki/The_Rathskeller