Why a prostitutes customer called a john?

The term "john" as a slang reference for a customer of a prostitute is believed to have originated in the early 20th century. It may have stemmed from a common practice of using the name "John" as a generic name for an unknown man, similar to how "Joe" is used in phrases like "Joe Public." Additionally, some theories suggest it could have originated from law enforcement or social workers using the name to anonymize clients in reports. The term has since become widely accepted in popular culture.