Yes, a question I can answer and the time zones are on my side for once.

The original meaning of moot was debatable, so a moot point was and still can be one that is debatable. The word was then taken over by law students to describe mock court sessions they used for practicing litigation skills. From that it came on to mean trivial, academic, irrelevant to the real world.

Bryan A. Garner's "A Dictionary of Modern Legal Usage" comments: 'Today in AmE, the predominant sense of moot is "having no practical significance" in both legal and nonlegal writing. ... To use moot in the sense "open to argument" in AmE today is to create an ambiguity, and to confuse most of one's readers. In BrE, the transformation in sense has been slower, and moot in its older sense retains vitality.'

Bingley

Bingley