It has to be remembered that Pete Seeger's Where Have All The Flower Gone? is based on the song fragments at the end of Mihail Sholokhov's Quiet Flows the Don.

Reworking of texts is a common practice amoung songwriters. This would make an interesting thread, comparing lyrics to sources.

Jean Ritchie's family folk song Nottamun Town was the tune Dylan used for Masters of War.

Tunes sources are easier to show than those for lyrics.

Stravinsky is attributed with this, to paraphrase, that composers don't waste time with plagiarism when they can outright steal.

Probably this would apply to lyricists. I think that it's not so important as to where the lyrics come from as much as how they express ideas with originality and flair. Gotta' give that to Dylan.
And to Woody. (Check out Buffalo Skinners).

None of this disturbs me very much because some call it the folk process. It ain't about who started it but who tells it best.

Frank Hamilton