What is Un-ass?
Un-ass meaning To let go of, give up, or share something. The concept is that you keep something precious (that you don’t want others to have or share) somewhere away from prying eyes (such as, theoretically, in your ass). Usually used in the form of a demand that you share something (like geedunk), as in ‘Un-ass, motherfucker!’ Another definition comes from the old horse US Army. Un-ass would mean to remove the item from the ‘ass’ which would be the pack animal.