Why do American people call trousers pants?

Just interested to know why, when we (UK) call pants what you wear UNDER trousers.
It's all about the names for men's leggings. We used to have pantaloons, that was one sort, and trews, I think they were another. In the UK, we went more with the word trews, and made the words trousers, whilst we modified the word pantaloons. The proper word is 'underpants', right? In other words, what we call 'pants' is what we wore under the pantaloons.

In the US however, the word trousers didn't catch on as strongly. They kept 'pants' instead, a pure shortening of 'pantaloons'- this must have been more natural, and perhaps as a result, to stop confusion, they stopped using the word 'underpants'- I don't know what they say for that though, maybe it's the same after all. The distinction is clear for them however. Gradually, it'll get that way for us too perhaps. My friend naturally says 'pants' instead of trousers, he's half English, half Italian. Perhaps the reason that the word 'pants' caught on rather than the word 'trousers' is down to the influx of Italian immigrants to the US? I can't say for sure, but the difference is basically down to a natural linguistic divide between US English and UK English, probably in the past couple of centuries.

Right, some other people are saying they call trousers pants. maybe that's just a gender difference? Girls underwear is definitely knickers- perhaps the word trousers is more of a masculine thing, and girls say pants to differentiate? It could also be language change in action, can't rule that out. maybe the difference will disappear completely in the next fifty years?
Why do english people call retards "chavs"?
its just a way of speaking. in my opinion, pants is a lot easier to say than under trousers. i happen to like that my diction can take short cuts. not to mention, the US split from britain to be different, not so that we can share the same of everything, otherwise, what wouldve been the point?
im english and i call trousers pants! i call what i wear under my pants knickers!
i *** fum the uk. but they call it pants
Well I used to live in India, where we speak British English, before moving to the US.Anyway they mix up a lot of things..like.
Football, the call it soccer
Biscuits, they call it cookie.why cookie.
rugby like game.football

lets just say Americans are backwards.
I'm American, my parents are from England. We lived in England for a while, and my youngest son started school there. After we moved back here, he insisted on everyone calling pants "trousahs" and sneakers "trainahs". It was very cute.

I don't know why we call them pants, sorry!
Well it's the difference between BE(British English) and AE(American English).I don't know who made the difference.
It is not just the Americans! I am English and as far as I am concerned Trousers are trousers , pants / knickers are trousers and knickers. I have a friend from Namibia who keeps refering to her pants , and always raises my blood pressure! Why cant knickers be knickers and trousers be trousers??//
Because they are foreign, and they do things differently. Also, they possibly tried to distance themselves from all things European.
Americans call trousers "pants" because the word "petunia" was already being used.
because we can and were cool like that
"because we can and were cool like that."

Sorry, I didn't understand that. Do you mean you were cool but aren't anymore?
if a garment having 2 long legs is called a pair of pants, if you cut one of the legs off, would the thing you have left be a pant? what about the one you cut off, would that be a pant too?
If you have underpants, what are they under? Pants.
In England, Pants is now an alternative word for 'Crap' meaning not very good.

"That whole song was pants!"

But I propose that Trousers should mean something that is REALLY crap.

"That song was TROUSERS!"
Simply because they can't speak the Queens English properly!
comes from the frence Pantyaloon, but most American call trousers as the bottom half of a suit and Slacks if thay are just bought on their own.
Because they can't speak English properly.
We as South Africans use it as well.

I don't know.maybe because we were taught that way?

It's still funny for me calling pants (meaning trousers in the UK,now)trousers.

I'ts like.I don't know..

Ah,if you were taught all your life,that something was called that way,and you go to another place,where things are different,then you will also be confused.

Ah,I've been in embarrasing sitiations,where I used the word pants,but meant trousers..
Yes - South African's also called trousers "pants".

After nearly 10 years living in the UK am still getting used to it!

And why to the English call panties "knickers"? That word always makes me giggle. :-)