To perform the nightmare flip aerial trick, the skateboarder kicks his board in order to make it flip 720 degrees along the board's long axis, while turning in a 180 degree motion toward the toe edge of the board, essentially combining a double kickflip, and a pop shove it.
Inventor
It was most likely invented by Rodney Mullen, an early skateboarder. However, it is also possible that it is simply a variation on one of his tricks, created by someone else.