Good question. Did not know that though. I believe it's more associated with being cool. I do know it hasn't been around that long so that date wold seem right, along with the gesture it's self. I know some bend in as if to touch opposite shoulders when they do, do it then it's the hand explosion afterward with some making the noise of an explosion. They do have a tendency to go back in time and pick up on something and make it their own. The young, cool and creative folks always thinking of something. But as to it replacing high five, I don't think it has, because people do still high five when they are in favour of something as well as fist bump. It probably did result from folks who don't like germs also.