[tsimionescu]

An even more iconic example is the anti-fascist song, Bella Ciao. That actually started its life as a worker's protest song of the same name but with very different lyrics, 50-80 years before its use at the end of the second World War.

Does that detract in any way from the anti-fascist song? Of course not. Folk music has always done this, and that has never taken anything away from its creativity (talking about actual folk music with collective authorship, not commercial music in the "folk" style).