I wonder where it originated, because it's a rhythm everyone knows. It's just a cheering type of thing, I guess, as Kinix said. People use it at football games and stuff and Ayu (and her Hamo Hamo Boys and Girls) used it for a friends-having-fun-at-the-beach-y feel. It's neat, cos I had that song playing once, and my friends (despite not knowing Ayu) clapped along like they knew the song already! ^_^