I've been reading the Smoky Mountain Hiking Clubs books from the 40's and I think it refers generally to the area, and more specificly where there are Thick Briers. The areas they were talking about being thick were areas that were logged and I'm sure had much more light & much more Briers than there are now. Not that the Smokies "lacks briers" of anything. Since the Cabin in the Brier was up Porter's I'm sure that area must also be included
Just my 2 cents.