This nunchaku trick is like the normal figure 8 nunchuck swing, but with two variations. The first variation is to swing the nunchaku up spin instead of down spin (the most common figure 8 that people do with chucks is down spin), and the second variation is that the grip is back grip, this means with the thumb being pointing to the tip of the nunchaku stick, and not to the chain or cord.
Tutorial:
Slow motion: