Used as a nick-name. 'Dizzle' is an alternative slang word for 'dogg'. Dizzle or 'Dogg' means a friend or buddy. This term came from the expression "dog is man's best friend". The letter 'j' at the beginning represents the first initial of the persons first name. The initial at the begining is not limited to one letter, but could also be substituted with a nick-name or birth-name.
Yo, my name is Jason, my friends call me J Dizzle, but you can call me Daddy.