I was looking up Redneck 'stuff' for another website and decided to find out about the origins of the term. I was surprised to find that the (or one of the) earliest references to the name as it's present definition in American culture was from 1893 (1): "...poorer inhabitants of the rural districts...", yet there is evidence of a much earlier usage of the term in both Scottish and American history.
The term refers to the Scottish Covenanters of the 1600's, those whom opposed taking the Church of England as the official state church (the political union of Scotland with England did not occur until 1707 when the United Kingdom of Great Britain was formed, prior to this Scotland was an independent sovereign state). The Covenanters held that Scotland desired a Presbyterian church government and signed documents to that effect in the mid 1600's, often using their own blood to sign. Many Covenanters wore a piece of red cloth around their necks as a sign of their position and so the term Red Neck became slang for 'Scottish Dissenter'.
As the union with England became inevitable and executions without trial reigned, many Covenanters fled to Ireland and North America setting up new Presbyterian Churches where they settled. The Dictionary of American Regional English (1) shows the earliest American citation of the term Redneck's used as a name for Presbyterians is from 1830: "...the Presbyterians of Fayetteville [North Carolina]".
There is also a Scottish origin for the term Hillbilly, which I may come back to later in time.
(1)Frederic Gomes Cassidy & Joan Houston Hall, Dictionary of American Regional English, 2002, pg 531