> Didn't the Appalachian people speak a rather Shakespearean dialect until fairly recently?
No. This widely-repeated myth is a real pet peeve of mine. Appalachian speech has some old-fashioned features, but how on earth could it be "Shakespearean"? There were no surviving English colonies in Shakespearean times; the region wasn't even settled until the 18th century and when it was, it was settled mainly by Scots and Ulster Scots, who hardly would have spoken in Shakespearean tones.