The story goes back to medieval England.
In the 1300s, English courts had a strange legal trick. When lawyers needed to test a case or file a claim involving someone whose identity was unknown, they used fictional names. The most common ones were John Doe and Richard Roe.
They were never real people just placeholders for "someone."
Centuries later the legal system kept using them, especially when the identity of a person was unknown. Hospitals used it for unidentified patients, police reports used it for unknown suspects.
Then tech borrowed the idea.
When developers needed a safe, neutral name for examples in forms, documentation, and test accounts, they adopted the same placeholder the legal world had used for hundreds of years.
That's why in almost every signup form you'll see: Name: John Doe
A 700-year-old legal tradition quietly living inside modern software.
Funny how the oldest traditions end up inside the newest software