These Scottish Presbyterians migrated from their lowland Scottish home to Ulster (the northern province of Ireland) during the 17th Century and soon settled in considerable numbers in North America across the 18th Century. One etymological theory holds that since many Scotch-Irish who settled in what would become the South were Presbyterian, the term was bestowed upon them and their descendants
Most of the traits that we associate with American "rednecks," particularly those in the upper South and Appalachia were inherited from the Scotch-Irish. This includes a great deal of their slang (where else in America are turtles called 'terpins'?), their anti-government attitudes, their violence and clan feuds, and their devotion to religion (although most of them moved from Presbyterianism to Methodism or Baptism).