It always irks me going to the UK hearing underpants referred to just as pants. I know that it’s just a regional difference, but still. It never made sense to me to call underpants pants, and then all pants trousers. Then it came to me…, by limiting the word pants to just underpants, there is then no way to refer to the entire set of non underpants below waist clothes. See, in US English, pants can refer to trousers, jeans, cords, sweatpants, slacks, shorts, parachute pants…whatever. With underpants being clear because they go under pants. With UK English, this doesn’t work. With pants relegated to meaning underwear, there is no word equivalent to pants in US English to refer to pants as a whole. You can refer to trousers as trousers, jeans as jeans and so on, but there is no word to refer to pants as a whole unless you go with trousers, which can be ambiguous. This is obviously a meaningless point as everybody understands each other and this problem never comes up as it is always obvious what is meant in context. Still, I think it’s interesting that one word for underwear can be said to have a disadvantage at all, as more often than not different words have no difference except as a result of perception.