How did John Wayne get the nickname “Duke”?

Marion Robert Morrison (May 1907 - June 1979), known professionally as John Wayne and nicknamed “Duke”, or “the Duke”, was an iconic American actor who gained popularity through his starring roles in Western and war films during Hollywood’s “Golden Age”, a period of classical American cinema which lasted from approximately 1915 to 1963,

The source of John Wayne's nickname is actually rather touching. As a child, he had a large dog, an Airedale Terrier named (you guessed it) Duke. He clearly loved both the dog and its name, because he embraced the dog’s name as his nickname.

Wayne was born in Winterset, Iowa, but grew up in Southern California. His father, a pharmacist named Clyde Morrison, moved the family to Palmdale, California in 1914. Two years later the family moved again, this time to the city of Glendale. Young Marion attended the local grade school and Glendale Union High School, where he performed well in sports and academics.

A local fireman at the station on his route to school in Glendale started calling him "Little Duke" because he never went anywhere without his huge dog, “Big Duke”. Soon others around town began calling the duo “Big and Little Duke” as well. Wayne preferred "Duke" to "Marion", the nickname stuck into adulthood, and he took it with him to Hollywood.