It's called using a nickname rather than a proper name.
Charles Rooke goes by Chuck, and Chuck Chuck.
The name Chuck is a diminutive form of the name Charles. It is commonly used as a nickname for someone named Charles or a variation of Charles, such as Chuck being short for Chuckie.
Charles 'Chuck' Tatum was born in 1926.
Charles 'Chuck' Harrison was born in 1931.
Charles Wayne 'Chuck' Day died in 2008.
Charles Wayne 'Chuck' Day was born in 1942.
Charles W. 'Chuck' Durham died in 2008.
Charles W. 'Chuck' Durham was born in 1918.
Charles (Chuck) Darwin
That's like asking why is Jimmy a nickname for James? Someone thought of Chuck a nickname for Charles and that's how it is. If you want my honest opinion, Chuck is a horrible nickname. Charles sounds way better.
You can use beef chuck or brisket as a substitute for beef shank in this recipe.
Charles vane