i believe that there are a couple different origins but its pretty blurry. from all the threads asking this same question i have seen a lot of different answers.
1) it came from skateboarding2) it came from snowboarding which got it from skateboarding3) jesus4) T HEED
and im sure there are many other answers but all of those are pretty common.
afterbang snowboard vid dropped in 02. most of you didnt know freestyle skiing existed then. travis heed was the first skier to have style, and he did afterbang, but that was his steeze, he wasnt trying to do it. theed is still waiting for the rest of the industry to catch up to him before he starts skiing again...