Aetna Mountain in Tennessee.
Pronounced "ET-NA" AFAIK.
Probably named because those are some nasty ass hills and it takes a pretty special buggy to make it up them... Mainly low, long, big tires, big motor, and lots of skinny pedal.
It's redneck as hell, but damn it looks like a lot of fun :) This is by far my favorite video of one of them in action:
http://www.youtube.com/watch?v=F6qQ4yKhmi4