A folk song is a variant. It travels through different incarnations. It invariably winds up different than when it started. It's usually not attributable to any singlw author. I think it's possible for a song to travel in tradition quickly but it does take time to emerge in various forms and be perpetuated by people from different cultures or in the same culture. I don't think you can put a time restriction on it. It could take decades, centuries, eras but it's not a written song over night.

Frank Hamilton