TextileGlossary.com

Pants are clothing for the lower body; the term comes from pantaloons. In Canadian, Australian and American English, the term pants refers to a long outer garment worn over the hips and legs, which in British English are called trousers.In British English, the term pants refers to men's underpants. It is a catch-all term that can denote anything from thongs to boxer shorts, but all have the common feature that they are worn under trousers. The word "pants" has acquired humorous connotations in the last few decades, largely among younger people. Many stand-up comedians have used the word as a lightly pejorative term. There is a tendency to use it as an adjective. This usage came to wider attention when it came to light that the then Prime Minister John Major tucked his shirt into his underpants.

an outer garment covering each leg separately and usually extending from the waist to the ankle [Usually used in plural]; [Chiefly British] men's underpants; [Plural] pantie