This phrase is probably one of the most misused in the English language. Often, people will say a mute point instead. There are a few reasons for this, I believe:

1. It’s used more in discussions than in written English, so many people don’t know how to spell the word.
2. Mute is a much more common word, and kind of makes sense in the context: if a point is moot, it doesn’t need to be mentioned, so it’s mute, or silent.
3. What the bloody hell does moot mean anyway?

That’s an interesting question actually, because it’s not quite as simple as you might imagine. The Oxford English Dictionary’s second listed meaning for moot is having little or no practical relevance, which is how it’s commonly used, e.g.

Whether  they were the better team or not is a moot point: the match is over and they lost.

But the first meaning in the OED is subject to debate, dispute, or uncertainty. Which of course is the exact opposite of how we mostly use the term. How on earth could this be? To solve this mystery, we have to delve deep into the origins of the word moot…

The word first came about as a noun in the 12th century, derived from Old English and Proto-Germanic origins. It referred to a meeting or gathering of councillors or general community leaders, usually to discuss important matters (and is also the origin of the verb to meet). If you’re familiar with The Lord of the Rings, you might remember the Entmoot in The Two Towers: when all the Ents (big talking trees, basically) gather together for a lengthy discussion. If your taste in fantasy is more modern, you might remember the approximately 5,000 chapters about the Kingsmoot in George R.R. Martin’s A Feast for Crows.

In the 16th century, the term moot case began to come into usage. This referred to the practice of law students who would gather together in large groups in “moot courts” to discuss hypothetical cases. A moot case thus came to mean a case subject to debate, dispute, or uncertainty, just like one that would gather lots of students together to discuss.

How then could moot also come to mean having little or no practical relevance? It’s not clear exactly when the shift occurred, but it’s generally believed that this meaning came into existence due to the purely academic, hypothetical nature of moot courts. Yes, they were very useful and relevant for the students involved, but compared to real cases, they were irrelevant (also consider how we say something is academic if it’s moot).

Which does make sense when you think about it, just as it equally makes sense that a moot point would also be one subject to debate or uncertainty. Sometimes a word can simply end up with contradictory meanings with perfectly logical explanations for each. At least nowadays in ordinary usage it really only means without practical relevance, so worrying about whether or not someone will understand you is a moot point, really. Just not a mute one.