I'm a Spanish girl that is in England and I have problems with the two following phrases that recently I have listened and answered:
(a flatmate (girl) to all of those who were about to go out) 'You got your knickers on? (I said that I don't wear knickers and the girl started laughing of me - why??:S)
(the same flatmate to me) 'don't be such a stroppy knickers'