NYT has a big article on the on the Wisconsin-Nebraska game, with copious info about the "Jump Around."

The origin, the history, the engineering. It's all here:

In 1998, during the first night homecoming game for Wisconsin, Kluender was looking for something to keep the crowd energized between the third and fourth quarters. He had a list of suggested songs provided by Ryan Sondrup, an intern in the marketing department and a former Badgers football player. Kluender chose “Jump Around” and looked away from the field to check his notes. When he turned back he said the leaping students looked “like popcorn popping.”

Much, much more at the link, such as why you don't have to worry that all that shaking won't collapse the stadium. (People feel like the deck is moving up to 10 inches, but it really only moves 0.4 inches, and it would have to move 12 inches to cause any damage, but movement like that would make everyone fall down, in which case they would not be jumping around.)