LOL - Well, I don't know either why is that so. I just assume it might be because at the very beginning many members were able to reach the Minnow level quite soon and all the discussions going around at that time were in comparison in between Minnows and Whales (like there is no level before Minnow and no levels in between minnow and whales). So, I think it gets sneaked in the common vocabulary that way.