This is one of the most famous expressions that is attributed to a fanciful (i.e. false) origin. Mentalfloss.com explains the tall tale is that digging up coffins to reused grave space found many with scratch marks, which indicated the people were buried alive. The alleged solution was to install a string to the wrist of the corpse and attach it to a bell. People sat in the graveyard to listen to a bell ringing as a plea for help. The truth is that a “safety coffin,” which monitored the corpse for movement and triggered a bell and waved a flag, was patented in the 19th century. The expression actually originated from substituting a look-alike horse in a race or athlete in a sporting event. The talented look-alike was the “dead ringer.” “Dead” refers to “absolute, exact, complete” while “ringer” originally was the person arranging the swap and later came to mean the substituted competitor.