:biff: /bif/ vt. To notify someone of incoming mail. From the
BSD utility `biff(1)', which was in turn named after a
friendly golden Labrador who used to chase frisbees in the halls at
UCB while 4.2BSD was in development (it had a well-known habit of
barking whenever the mailman came). No relation to
{BIFF}.
-- The AI Hackers Dictionary