It's the junk in your trunk man. It's what you put your mug on and saddle up and ride. It's an ass. You guys are dumbasses, it isn't dadonkadonk, it is badonkadonk.
A butt so large and juicy, but yet thick and strong. It is like that of a large wild animal. From the root Native American word "Tatonka", meaning large bull.
As "Tatonka" was used in the movie dances with wolves, Dadonkadonk is the only word needed to communicate between cultures.
