Sounds dumb and I've never heard it before.
I was listening to some 2009 bombcasts and they used it, so I bet you've heard it before. Brad had discovered LOL and HON. MOBA hadn't been an established term yet. They were talking about possible names for the DOTA clone genre and Vinny suggested Hero Action Game, which they rejected because it was too similar to the already existing Character Action Game.
Lords Management, please