Hi, Beginner. I finally looked up "The Hern." As TheSnail already mentioned, that is also known as "The Corpus Christi Carol."

I studied that in college, in a course in medieval literature. That poem has haunted and mystified people for centuries. But I don't believe it ever evolved into something else. It was and remains medieval. It belongs to an era of huge (and frightening) forests, deep Christian faith, and belief in magic. A modern person may perform it, but it remains a medieval work.

Upthread I mentioned the song "I gave my love a cherry." A version of that poem was in the very college textbook that had the Corpus Christi carol. That is a song (or poem) that has evolved.

As somebody pointed out, we can follow lyrics through time much better than we can follow melodies.