Mening Of Black Wrist Band What Is The Reason Behind Naming Some Englishmen As Mr. Long, Mr. Black, Mr. Water Etc?

What is the reason behind naming some Englishmen as Mr. Long, Mr. Black, Mr. Water etc? - mening of black wrist band

In relation to them, I curious. As words like black, long, water, rain, the furnace is a normal mening be (their names for the same reason that is) always say the same thing? Or is there something behind their names?