Do I remember aright that "sawmill tuning" was for Clarence Ashley what John Cohen said Roscoe Holcomb (I think) called "lassie-making tuning"? Generated some heh-heh speculation amongst us urban folkies, but turned out that "lassie" referred to molasses (not mole-asses, either), having something to do with the tuning being associated with particular banjo song(s?) often played/sung when the molasses-making process was under way on the farm. (But check with John Cohen to see if I'm inadvertently inventing folklore here.)

And is it sawmill tuning because it makes the banjo sound even more like one than usual?

Ashley's tuning for "Little Sadie" as well as for "The Coo Coo Bird" (spelled that way on a record -- Folkways' Harry Smith (ed.) Anthology of American Folk Music).

-- Katmuse