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 Rooke goes by Chuck, and Chuck Chuck.
Charles 'Chuck' Tatum was born in 1926.
Charles 'Chuck' Harrison was born in 1931.
Chuck is generally a nickname for "Charles."
Charles Wayne 'Chuck' Day died in 2008.
Charles W. 'Chuck' Durham died in 2008.
Charles W. 'Chuck' Durham was born in 1918.
Charles Wayne 'Chuck' Day was born in 1942.
His real name is Carlos Ray Norris. The nickname 'Chuck' was given to him by his friends when he was in the Air Force, since Carlos is the Spanish form of Charles, Chuck being short for it.
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.