Why do we refer to some singular articles of clothing as a “pair?” Like a pair of pants or a pair of underwear?

Question

Why do we refer to some singular articles of clothing as a “pair?” Like a pair of pants or a pair of underwear?

In: Other

Answer 1

Because they used to be two separate pieces with no crotch seam connecting them! [https://www.worldwidewords.org/qa/qa-pai1.htm](https://www.worldwidewords.org/qa/qa-pai1.htm)