The term “Hill-Billies” is first encountered in documents from 17th century Ireland, according to Wikipedia. Roman Catholic King James II landed at Kinsale in Ireland in 1689 and began to raise a Catholic army in an attempt to regain the British throne. Protestant King William III, Prince of Orange, led an English counter force into Ireland and defeated James II at the Battle of the Boyne in 1690. A significant portion of William III’s army was composed of Protestants of Scottish descent (Planters) who had settled in Ulster in northern Ireland.
The southern Irish Catholic supporters of James II referred to these northern Protestant supporters of King William as “Hill-Billies.” and “Billy Boys”–Billy being an abbreviation of William; the term “Billy Boy” is still used today, mainly in Northern Ireland. The Catholics and Protestants were at war and the terms were not spoken in kindness. Supporters of King William more generally came to be known as Orangemen.
The first US published reference to the word ‘hillbilly’ appeared in 1800 in the New York Journal. The paper described the species as “a free and untrammeled white citizen of Alabama, who lives in the hills, has no means to speak of, dresses as he can, talks as he pleases, drinks whiskey when he gets it, and fires off his revolver as the fancy takes him.”
The image stuck. “In subsequent centuries, even after the mountains came to be cherished for their awe-inspiring beauty and appreciated as places of inspiration and recreation, mountain dwellers themselves never fared as well as the scenery,” states the “Encyclopedia of Appalachia,” published last spring by the University of Tennesse Press.