Well if I may, I'd just like to drop in with a deep and meaningful point:

Within the UK the term 'Pants' can be used for either trousers or underpants. It depends on where you are. Growing up in Lancashire I was entirely familiar with the use of both trousers and pants synonymously. Not until I arrived at Uni did I come across the usage of 'pants' for underwear.

Interestingly I think it would be true of my experience to say that by far the most common usage of the word 'pants' that I heard in my Uni days was as an adjective or exclamation. "That film was utter pants!", or, "Pants! I forgot to finish my thesis!".

Just to let you know.