Line from Die-Hard "Yippie Kai Yay"

A friend of mine started this. We were having a conversation at noodle shop and the topic was about a famous line from Die Hard. Bruce Willis' character usually says this in the movie. Its "Yippie Kai Yay". When he asked me about this, I didn't think it was an English phrase. I wasn't really sure and made a search on the internet. Here's what I've found.

In the original film, John McClane was talking with the main villain via a walkie-talkie. The main villian asked him if he was trying to be like John Wayne. Bruce's character replied that he was always partial to Roy Rogers, who's catchphrase was "Yippe Ki Ya." McClane added the motherf#$%$er part. [via Yahoo Answers!]