When you were young, did you ever play the party game "Pass-it-on"?    This is probably the same effect when singing troubadours, traveling the countryside, would  pass on their songs to someone along the way.    Although the person would  remember the catchy tune, they might forget the exact words and substitute them with something similar.

At the time I began my research of this song, I was surprised to find so  many versions.   In my youth, my mother played the piano at family gatherings and the relatives would  join in singing the song, Barbara Allen (at that time it was Barbara Ellen).   All I remembered  about the song, along with the melody,  was that every stanza ended with: "Oh cruel, cruel Barbara Ellen". . . I haven't seen  that particular version in books or on the internet.

To my knowledge the author is unknown,  and the ballad originated sometime during, or before, the 17th
Century, either in Scotland or England.  The version that I have added here is one from the 17th century.

If you forgot the tune, click to listen: Barbara Allen Melody

NOTE:   Midi sequence name: Barry Taylor