What is the Origin of Michigan hillbilly?

Answer 1

As it was told to me, the name had it's origins in Ireland, from the 1690 Battle of Boyne between the armies of Protestant King William of Orange and Catholic King James II. The victory of King William's army was credited with ensuring the dominance of the Protestant faith in Northern Europe.
The early Protestant settlers in America, coming from Scotland and Ulster, celebrated annually that
victory by King William, also called King Billy and were called "billys" or "billyboys".
The Ulster-Scots or Scots-Irish migrated from Pennsylvania south into the Appalachians and those were commonly called "hillbillys".
I have found nothing documented that explains the name's origin but this is what my grandmother told me.
Does anyone know something about it?