Every so often, a skilled communicator chooses to bend a rule in order to make a point. If the point is well made, it sticks, and people start imitating it.
Next thing you know, the newly-coined word becomes an "actual" word with real currency. (I put "actual" in quotes, because if you think about it, all words are made up. All "rules" are really just general guidelines.)
http://blog.xkcd.com/2015/09/22/a-thing-explainer-word-check...
Of course now that you've raised the point, I'll probably have to waste some time today working out a simple word name for myself.
> I found myself wishing that Munroe had allowed himself a few more terms—“Mars” instead of “red world,” or “helium” instead of “funny voice air.”
By contrast, go is such a foundational word to English that it appears in English reading primers for toddlers, and a goer goes.
The point is, he's not simply stemming. He cheats.
I certainly think its clear (and even implicit in his own descriptions) that the exact methodology is not disclosed, but I don't think its far to say simply "he cheated".