Some of these are still around I think. Somebody in the linguistics world should catalog this stuff, and research it’s possible origins. Well, they probably have.
dang – exclamation meaning “wow”
duh – verb? noun? what the hell is it means “you or I is a dumbass”
kick ass – another exclamation essentially meaning “that’s really great”
decent – see “kick ass”
tough – see “decent”
You will now discuss and augment.