I’ve looked everywhere but cannot find the origin of moot.
Well, dear, we’re afraid you didn’t look quite everywhere, because the origin of moot isn’t that difficult to find. However, we’ll make it easy on you. Moot dates back to Old English, where we find it in such words as Witenagemot, the Anglo-Saxon precursor of today’s Parliament (literally “meeting of wise men”). Mot basically meant “meet”, and it comes, in fact, from the same source as today’s word meet. That common source was the prehistoric Germanic word *motam “meeting”. So a moot point is a point that is discussed in a meeting. At least that’s what it was originally. Today the meaning has been corrupted to “no longer important, irrelevant”. How did this happen? It is probably a result of the mistaken interpretation of the word moot in a legal sense. Moot court is the name given to a legal exercise wherein a hypothetical case is discussed and debated. In the end, because the case is hypothetical, it is “irrelevant”, and so moot took on that meaning over time and that, today, is the more common meaning, even though most proscriptivists consider it incorrect.