(n.) a local assembly or council meeting; a point up for debate
A moot is a council meeting—and a moot point was originally a hypothetical point set up for debate by a meeting or ‘moot’ of law students.
The word moot itself is an Anglo-Saxonism, dating back to the very earliest days of the English language; a council meeting or assembly would have been known as a mot in Old English.
Through its even earlier Germanic roots, moot is unsurprisingly a none-too distant etymological cousin of meet, and has cognates in a number of the modern Germanic languages, like Danish (møt), Swedish (möt) and Icelandic (mót).
The first moot points meanwhile date back to the early 1500s, when groups or ‘moots’ of law students would come together to debate (often purely hypothetical) judiciary points and cases as a means of improving their study of law and their rhetorical prowess. It’s from these meetings that moot also later emerged as a verb, meaning ‘to put forward as a suggestion’, or ‘to argue for and against’.
As a more general word for a meeting or assembly, moot is used somewhat less frequently today that it once was, but still survives of course—indeed many towns and villages still have moot halls, where local meetings and council gatherings can still take place.