Ooh of course it's the waving prarie grass, and the white yarn represented the purifiacation of the dance circle.
For real though, I made it up. And yours doesn't seem to have much truth in it either. C'mon the roach was around long before competion powwows.
Anybody know if maybe it's like a chiken dancer's feathers? They look simaler maybe a grass dancer forgot his feathers and put those in? If he won well people imitate champions. This is just a suggestion I bet people realy don't know. I'm sure somebody out there could give you a vague area of origin and time, but they haven't answered yet.
And steve we should write a book of these great stories and sell it, we'd make a fortune. Make a lot of people mad in the process but it seems everyones getting rich off of native culture but, the people who should be. Call me we'll get an agent, we'll be bigger than Harry potter.