Saved By the Bell

In 17th century England, a guard at Windsor Castle was accused of falling asleep at his post. He claimed he was wrongly accused and could prove it; he had heard the church bell chime 13 times at midnight. Townspeople supported his claim and he was not executed. Today we think of the bell that ends a round in boxing, often saving the boxer from injury, or the bell at the end of a class period, saving you from more work. Regardless, this idiom means rescue from a situation at the last possible moment.