Take a look around you and see how industrialized and complex our civilization and society are. It wasn't always this way. Humans used to not be able to do things that we consider basic. One of those things is communicating. Ancient humans had extremely rudimentary ways of communicating that limited them severely. As a way to adapt and overcome their environment, they had to develop their own language in order to communicate more effectively. Language is thousands of years old so, we don't know where every word ever comes from. However, as according to research by ancient historians and linguists, the word "mediocre" was invented by ancient humans as a response to playing this game.