1. It's a sentence from Rome slang. It means a self-important persone, but in fact, a
guy no one knows coming from a
little town no one knows.
2. It could be used also to say "you know very
well who"
2. A husband comes back home and shuts the
door. The
wife asks: "Who is?" - the husband: "Fra Cazzo
da Velletri" (= who else do you wonder it could be?)