This is a term I grew up hearing in reference to whenever we were homeward bound and moving perhaps a bit faster than we should have been. I think it's original reference was used to describe a horse who could sense the moment you turned it back toward home and would move at an incredible fast (and sometimes uncontrollable) pace. I got to experience this first hand and can say it was not a good experience ... it ended with me flying off of the horse :)
Anyhow...we are homeward bound for Christmas and are most definitely feeling barn sour. We've got about 15 flight hours in our future and another 8-10 hours of hanging out in airports, but what's important is that we're heading to family! Whoo-hoo!!