English police officers are known as bobbies because:

The name "bobbies" comes from Sir Robert Peel, who established the Metropolitan Police Force for London in 1829. He is often referred to as the father of modern policing and his last name, Peel, was used to create the informal term for police officers.

English police officers are known as bobbies because of the nickname given to the first professional police force established in England. In 1829, Sir Robert Peel established the Metropolitan Police Force in London, which became the model for modern policing. The officers of this force were called "Peelers" or "Bobbies" after Sir Robert Peel. The nickname "bobbies" is still used today to refer to English police officers.