Here's what William Butler Yeats thought it was.

"Folk-art is indeed the oldest of the aristocracies of thought, and because it refuses what is passing and trivial, the merely clever and pretty, as certainly the vulgar and insincere, and because it has gathered into itself the simplest and most unforgettable thoughts of the generations, it is the soil where all art is rooted."

I agree with him. I underscore the word "generations".

Frank Hamilton