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Pants are a singular object. Then why do we say “pants” instead of “pant”?

It’s a common vagary of the English language that pants—or trousers, slacks, khakis, shorts—is always presented as a plural. It’s never pant, but rather a pair of pants. Always in the multiple. But why? Pants are clearly a single object. One could argue that they have two separate areas for one’s legs to go. Or because legs are themselves two independent objects that the pants fit the plural. (It would be kind of weird to talk about putting “pant” on your “legs.”)
But this is a grammatical fallacy. A shirt is just pants for your top half, and that’s a singular object, even though there are holes for each of your independent arms in which to go. Either shirt should be called shirts, or pants should be called pant. But it’s not. It’s pants. (And multiple pairs of pants is also called “pants,” which just confuses and obscures the issue.) So then why are pants plural?
From its inception in English, pants has been plural. It’s a shortened adaptation of pantaloons, those tight-like leg coverings worn by pirates and Shakespearean characters. And in those eras of 300 or 400 years ago, before pants were a single entity, pants were actually two separate garments. A person would put on each leg piece separately and then wrapped or tied together at the waist.
Pants are part of a very small subset of plural English words in which they have no real singular counterpart. Almost all are similar examples of things that look like two objects that have been fused together to create one thing, but keeping their plurality, grammar-wise. For example: clothes, goggles, and panties.
However, the one place where pants actually are referred to in the singular is in the world of fashion. It’s a bit of a quirk, but high-end tailors and fashion magazines use “pant” and “pants” interchangeably.