Why is Bra Singular But Panties Plural?

The reason is that originally, underwear (or undergarments) was singular and came from the phrase “to go under one’s clothes.” But panties, originally pantalettes, were popular as a separate garment that would cover the legs as well as the crotch. Read more- https://www.fashionkund.com/why-is-bra-singular-but-panties-plural/