Definition & Meaning of "mucker"in English

What does "mucker" mean in British slang?

The structure adds the "-er" suffix to "muck" (dirt or mess), possibly from the idea of working together in mucky conditions like a mine or farm. It is used in British English, particularly in Northern England and the Midlands (especially Yorkshire, Lancashire, and Nottinghamshire), to refer to a friend, mate, or companion in a friendly, informal way. People typically say "Alright, mucker?" or "He's an old mucker of mine." The term originated in 19th century working class and mining communities, where "mucker" meant a workmate who shovels muck (loose rock or dirt), and later expanded to mean any close friend.