(colloquial) saved or freed from an awkward
situation at the last possible
moment. The expression comes from the sport of boxing. If a fallen boxer does not
rise after 10 seconds have been counted, he is declared the loser. However, a former practice in boxing allowed the
count to be interrupted by the ringing of the bell which signaled the end of a three-minute
period in the boxing match.
—SHSBC Binder 20 Approved Glossary