I think I mentioned not too long ago that for a time I lived in Boston. It was on the green line (subway) and before I got the lay of the land, I would have to figure out where to get off the subway by the big Marty's Liquor sign. But one of the places I used to walk by (I had a lot of friends at BU at the time) was:
Rathskeller -- a usually basement tavern or restaurant.
I never went in, because I never really knew what kind of place it was. Turns out it was a pretty famous bar/concert venue. Apparently it closed in 1997. Too bad, because even though I didn't know what it was, I was fascinated by the name. But here's the kicker -- until today I never even looked up the definition, because I didn't even know it was a proper noun, I just thought it was something made up.