When our ancestors realized that they were burying a great deal of people before their time had actually come, they came up with a solution. They tied a string onto the "dead" person's hand, buried them, and tied the other end of the string to a bell and then tied it to a nearby tree branch. If the person revived enough to ring the bel, their survivors would rush out and dig them up. Hence..."saved by the bell." (Circa 1500s)
One part lazy, two parts eerie.