Burke, thanks for the notes on Walker. This has been a favorite Christmas song of mine for a long time. It plays nicely on the mountain dulcimer. It is very common for religious writers to adopt secular melodies for Christian songs. The Wesley's made no apologies for it. John supposedly said "Why should the devil have all the good tunes". What Child is This? using the tune of Greensleeves is another prime example. However, as Alex said for Christian writers to take a secular song and rewrite the words is a rare thing indeed. While I cannot think of an example, at present, I would not go so far as to say it has never happened.