The phrase the real McCoy was used extensively in my family when I was growing up. My dad would usually authenticate something by saying it was the real McCoy. One day while in the library I picked up a book on vignettes of language. The book was pocket-size and fairly thin, but contain a world of knowledge on things we hear practically everyday.

It's been sometime since I've read that book on vignettes of language, but when searching the web for reference material on this topic, I found this page