ah - light begins to dawn...

As I understand it (at least from what I can find out on the web) most of the "standard" carols are "a" version of a carol that was sung in multiple forms previously; they are beginning to fragment back into different versions here in the US - depending on what denomination's hymnal you learn them from - or which performaer's album! Get 10 people together to sing a carol and chances are you will end up with at least 5 versions.