Question: where did the expression dead ringer come from

title: Safety coffin
text: In 1829 , Dr. Johann Gottfried Taberger designed a system using a bell which would alert the cemetery nightwatchman . The corpse would have strings attached to its hands , head and feet . A housing around the bell above ground prevented it ringing accidentally . An improvement over previous designs , the housing prevented rainwater from running down the tube and netting prevented insects from entering the coffin . If the bell rang the watchman had to insert a second tube and pump air into the coffin with a bellows to allow the occupant to survive until the casket could be dug up . Vester