The article by Uncle Bob says this about the "stub" twist. I guess he, at least, thought this.

"The stub and twist barrels were made from stubs of horseshoe nails brought in by the country blacksmiths, hence the name "stub" in connection with "twist", which later word refered to the grain of the barrel which twisted around in a spiral form from the breech to the muzzle."

http://www.bakercollectors.com/