A pair of jeans. A pair of trousers. A pair of overalls.
I understand full well that a “pair” refers to a set of two. And indeed, pants have two holes – one for each leg. But when asked how we put our pants on we say, “I put my pants on just like everyone else, one leg at a time.”
We never refer to the singular “pant” or “jean” or “trouser.” No one would ever buy just one pant or one jean, it’s just silly.
Shirts have two holes, one for each arm, yet we don’t refer to it as a pair of shirts. Eyeglasses are referred to in pairs because of the fact that we have two eyes and there are two pieces of glass. But I can get on board with this because there actually is such a phenomenon as the singular eyeglass. So in my world a pair of eyeglasses makes perfect sense. A pair of gloves works for me also following that same reasoning.
Someone come up with how to wear just “the pant” and I will come up with some kind of prize for you. And yes, these are the types of things I think about while I’m at work.