I personally always thought "skadoosh" was supposed to be the onomatopoeia for Po's belly hitting stuff hard. I think they showed that in one of the film's first trailers, with Po hitting Tai Lung with his belly and saying, "Skadoosh."
I guess this video was mainly supposed to be a fun, insightful video around it, but I prefer sticking with my onomatopoeia theory. :P
Huh, interesting bonus feature, Thx for sharing it :)