A more thorough explanation:

John Doe is a fictitious name used in legal proceedings to refer to a person whose identity is unknown, to protect a person's known identity, or to indicate that a true defendant does not exist. It is often used in cases where the real name of a person is not known or cannot be disclosed for privacy or safety reasons.

For example, in a lawsuit where the identity of a witness needs to be protected, the court may refer to the witness as John Doe instead of using their real name. Similarly, if a person is suing someone whose identity is not known, they may name the defendant as John Doe until their identity is discovered.

The use of the name John Doe in legal proceedings dates back to the 18th century when it was used as a placeholder name for a person whose real name was not known. It is often used in conjunction with the name Richard Roe, which is another placeholder name for a defendant in a lawsuit.

Overall, John Doe is a useful tool in the legal system to protect the privacy and safety of individuals while still allowing for legal proceedings to take place.