Hi, Reinhard, I'm waiting for the noted Mudcatter, Mr. Nowell Sing We Clear, to drop by and comment. He hails from Connecticut or somewhere like that, but speaks with a pronounced British accent.
Sounds to me like the hymn has a solid Methodist pedigree, but came into general use as a carol in Sheffield. Note that the hymn tells the story of the Woman at the Well from the Gospel of John. It's not a Christmas story - but is it used as a Christmas carol?
-Joe-