What is a dead ringer?

A "dead ringer" is a slang term that refers to someone or something that is very similar in appearance to another person or thing. It is often used to describe someone who looks exactly like another person, or a situation that is very similar to another situation. The term originated in the 19th century and is thought to have come from the practice of placing a bell in a coffin to prevent premature burial. If the person was mistakenly believed to be dead and then later woke up, they could ring the bell to alert others that they were still alive. This person was said to be a "dead ringer" for the deceased. Today, the term is commonly used in informal conversation to describe a striking resemblance between two people or things.