Starting with a side slide, say from left to right, you would keep pressure on the right hand and a little more slack on the left. Increase the pressure on the right until the kite starts turning right into the ground. You should time it such that the right tip is about to stab the ground and then slack and pop the left wing in an exaggerated axel move. The right wing tip should drive into the ground and then kite should spring back up into an axel.
Executed well, the kite will spring high into the air with a resounding "thonk". If you're not so lucky, the kite might stay on the ground with a dissapointing "crack".
The name for this move, like the axel, comes from ice skating. The toe loop in ice skating is like the axel but starts with the skater driving the serrated toe of one skate into the ice to get rotational momentum. The similarities with the kite trick suggested the name was appropriate.