[The] carol was widely printed on broadsides and in song books during the 19th century, and has turned up in oral tradition in most places where English is spoken. The Shetland tune 'Christmas Day i da Moarnin' came from the repertoire of John Stickle (1875-1957) of Unst, and the family tradition was that it had been composed by his great-grandfather Friedemann Stickle (born in the 1780s), who was paid to play it every Christmas morning in the Ha' of Buness, the home of the Edmonston family at Baltasound.

Notation made by Patrick Shuldham-Shaw from John's playing (28 April 1947) was printed in the Journal of the English Folk Dance and Song Society, 9 (3) 1962, 140; but nowadays it is probably most familiar in the form recorded by The Boys of the Lough, which they got via Tom Anderson. Either he or they seem to have changed it rather at some point, if the 1947 notation is anything to go by (and Pat Shaw noted that Mr Stickle's playing was very consistent and that he was very insistent that the notation be exactly as played).

If there were ever any words sung to it in Shetland, they don't survive; though Tom Anderson apparently reckoned (quite reasonably) that the words of the title can be 'heard' in the final line.
By Malcolm Douglas edited 10 Sep 07 - 05:12 am on joe-offer.com/folkinfo