"Extensive research has been conducted since the 1930s to determine the origin of the Appalachian dialect. One popular theory is that the dialect is a preserved remnant of 16th-century (or "Elizabethan") English in isolation,[5][6] though a far more accurate comparison would be to 18th-century (or "colonial") English.[7] Regardless, the Appalachian dialect studied within the last century, like most dialects, actually shows a mix of both older and newer features.[7]"

[5]: Montgomery, Michael (1995), "How Scotch-Irish is Your English?", The Journal of East Tennessee History, East Tennessee Historical Society (67), pp. 17-18
[6]: Cooper, Horton. "History of Avery County", Biltmore Press, (1964)
[7]: Montgomery, Michael (2004), Bernd, Kortmann; Schneider, Edgar W. (eds.), A Handbook of Varieties of English, Berlin/New York: Mouton de Gruyter, p. 246

From https://en.wikipedia.org/wiki/Appalachian_English