While traveling to Aruba last year, we had the boys go and try kite surfing. There was a really nice dude helping both the kids and the guys. He kept on saying this word and we thought he was making fun of us tourists because we had never heard it in this form....we had heard hang loose or hang 10 so.... we finally asked:
The "shaka" sign is a common greeting in the Hawaiian culture, subsequently also used in surfer culture. The shaka sign, sometimes known as "hang loose", is a gesture of friendly intent often associated with Hawaii and surf culture.
Then we went a little further and found this clip from South Park...hysterical...ENJOY!