biff /bif/ vt.
To notify someone of incoming mail. From the BSD utility
biff(1), which was in turn named after a friendly
dog who used to chase frisbees in the halls at UCB while 4.2BSD
was in development. There was a legend that it had a habit of
barking whenever the mailman came, but the author of
biff says this is not true. No relation to B1FF.