An example of the sort of thing "jag" was talking about: Hamish Henderson collected a lullaby "Wee Davie Daylicht" in southwest Scotland and published it in "Tocher" with no information about its origins beyond the singer he got it from. In fact it was written in the 1920s (or maybe a bit earlier) and published in a book of songs of the "national" or "community" song genre.