Yes, I’m doing must this week. I think I had a reason why, but I can’t seem to remember it as I write this.
Must has a surprising amount of meanings—seriously, I’ve never heard of some of these. It’s apparently a word for newly fermented wine. And also a state of frenzied sexual excitement in large mammals, like elephants. I’m not kidding.
The must we’re most familiar with comes from Old English moste, which is the past tense of motan, meaning to have to. Before that, it comes from the Proto Germanic mot, where it means something like the ability to do something. It might come from the Proto Indo European med, to measure (and the origin word for medical), but that’s not for sure. Interesting if true, though.
There’s also musty, like a room shut up for too long. It showed up in the early sixteenth century. It’s not definite, but it may come from moisty (which was a word apparently), obviously coming from moist. And remember when I mentioned the wine definition of must? It comes from the Old English must, and before that the classical Latin mustum, which means both must (have to) and wine. And it’s also a possible origin for moist. See? Full circle! If it’s true!
Plus, like I said, there’s that whole “male frenzy” thing. We have Urdu to thank for that one. Must comes from the word mast, which means intoxicated, as it does in Persian, where Urdu got it from. Before that, it comes from the Proto Indo European mad, which means wet or moist, and is the origin word for mast. But not moist.
Finally, you’ve probably heard of muster. It showed up in the early fourteenth century, from the Old French mostrer, meaning reveal or appear. It didn’t mean assemble/gather until the early fifteenth century, though. Mostrer comes from the classical Latin monstrare, to show , and monstrum, meaning…monster. Didn’t see that one coming, did you?
Tony Jebson’s page on the Origins of Old English