The term recently came up in a thread, annoying many. A dirty little secret...I have been guilty of many "fastpacking" trips.
I'm completely ambivalent about the term; call me what you will. Maybe it's accurate in some circumstances. Maybe it's pure marketing hype in others.
I found a link to this article about the origins of the term on Anton Krupicka's blog today- it's from a late 80's issue of Ultrarunning Magazine.
I think claiming fame to coining a term is a little hard to prove, but it's a good article nonetheless.
...I'm sure Ray Jardine has claimed he invented and patented it somewhere ;)