Slurry way of saying "don't know". People either say it like that when they're feeling to lazy to speak properly or don't want to
speak at all.
Another reason is because they think
it's cool to use slang and miss-pronounce everything.
Example 1
Peter: "Yo comin' to da party ta-night?!"
Jase: "
Dun kno mann,think
imma be somewhier!"
Example 2
Hailey: "Hey, do you know where I put my keys? I had them just a-"
Carlos: "Dun know..(walks away)"
