Dead ringer is an idiom in English denoting a person or thing that closely resembles another. It dates back to the 19th century. [1]
In criminal slang, the practice of substituting a cheap item for a valuable one was known as ringing the changes (a phrase derived from campanology). [2] Those who practised this con were known as ringers. The term ringer was also used in horseracing, where it denoted someone who fraudently substituted one horse for another, as well as the horse that had been substituted. [3] Subsequently, it came to be used for anything that resembled something else, often with the addition of the adjective dead (meaning "exact"). [1]
The idiom is sometimes said to derive, like saved by the bell , from a custom of providing bell-pulls in coffins so that people who had been buried alive could call for help, but this is a folk etymology. [3] [4]