A Dead Ringer is a person who looks just like another person. In medieval Britain anybody found not to show signs of life was regarded as dead, when, in fact, they might have been simply unconscious or in a coma. There were occasions when bodies were exhumed later and the corpses found with their fingers worn to the bone, indicating they'd returned to consciousness and tried to claw their way out of the coffin. The image was so horrific that the English gentry began mistrusting medical opinions and would buried their loved ones with a length of string attached to their wrists, connected to a bell above the grave. A person returning to consciousness and finding themselves prematurely buried could attract attention by ringing the bell. It's been recorded this actually happened and worked. Many so called "bodies" were exhumed after bells were rung and some people carried on with their normal lives after having been once presumed dead. When spotted in the street, such people might provoke the startled words "That looks just like Samuel Smith- I thought he was dead!" to which they might receive the reply, "Yes, he must be a dead ringer".