He did invent it, or at least was credited with inventing it...those first black powder firearms you refer to were breech loading flintlocks that Henry Nock developed. He lived from 1741 to 1804. As to the etymology of the word, we could be here all day...like a great many other words and family names, the spelling and usage changed over the years. The literature is unanimous (as near as I've ever found anyway) in referring to it as a "knoxform" or a "knox form". Blackmore concludes his chapter on the breechloading flintlocks (paraphrasing here): "Henry Nock's name lives on in the knoxform found on modern service rifles"...I've butchered the quote, but the spelling is his.
Sums it up nicely I think...I think it's just a pretentious way of advertising that you really know where the term came from! To each his own...![]()