This is stretching the truth of the matter quite a bit. Nobody used the word that way since 1660 or so (which is quite a ways before the 1690's you speak of). The origins of this term as it is used today began in I think.. 1890-something, and it very specifically refers to the sun burning the poor working men.
Like almost everything that faux-Scottish wannabes in the US cling to, this, too, is 88% -------- tied together precariously with 2% genuine fact, and 10 percent misapplied history. For example: did Ulster-Scotts settle in the Appalachians? Absolutely! Did they call themselves rednecks? Absolutely not.
"Redneck" means exactly what Doc Sarvis, myself, and (statistically speaking) 100% of America thinks it means.
There used to be a douchenozzle at the local Costco who would wear a black kilt to work. He did it every day, claimed it was part of his heritage. When a man from Scotland asked him to explain himself, he pontificated and acted as if the Scotsman was his brother. When the actual Scot tried to explain to the wannabe how clans and kilts and whatnot worked (and how nobody wears them day to day anymore than Japanese men do kimonos), the wannabe tried to tell the NATIVE that he was wrong. The native explained his point twice more; once in the belly and once across the chin.
Dumbass hasn't worn a kilt since.