Witches knickers

This morning in my front yard, I kept hearing a rustling noise. I thought maybe my housecat, Kong, had escaped and was in the bushes. I finally figured out the noise was made by a plastic grocery bag caught in a tree branch. I was trying to remember a name for such a bag. Found this -- witches knickers. That sounds close. [Dead link removed - ed]

That was interesting, but a little disappointing. Several populations around the globe seem to have found interesting names for this phenomenon, but only in Alaska, apparently, have Americans found a colorful descriptive phrase for it. What, are we without linguistic imagination?
SS