There's a country of origin for that "sport"? I don't think so. It's something mildly similar to what me and my friends used to do at school, but the "competition" would last for days, weeks, months and years. Basically, while in the big group chatting away you slap one of them when they're least expecting and they'll end up getting you back at some point.
Really though, where's the fun in just standing there slapping each other? And surely one of them could have just given the other an almighty blow and knocked her to the ground.