Originated by the Infamous Mobb Deep, this slang term came about when Havoc(who has a speech impediment) couldn't pronounce "son" correctly, thus "thun" or "dun". Today, dun is commonly used in casual conversation quite flexibly. With a variety of meanings in various contexts, dun still translates as son among urban cultures. It is often used loosely as a reference to a person.
"...you better finish what you started dun."-Mobb Deep
"Yo, wassup dun? I heard them cats was runnin 13th and Prospect."
"I heard Marie just gave birth to your baby dun!"
"Yo, wassup dun? I heard them cats was runnin 13th and Prospect."
"I heard Marie just gave birth to your baby dun!"
by F.A. Rich a.k.a. MC Krewga April 8, 2004