In Harland and Wilkinsons 'Lancashire Legends' there is a play listed as 'The Pace Egg Mummers' which seems to be somewhat of a analogy, seeing as Pace Egg is at Easter but Mumming is a Christmas tradition. It is identical to the Lancaster and Abram Pace Egg plays but for mentions of Christmas. I think it shows that as far back as when Messers H & W were collecting these traditions there was a blurred line between them. If the play, song or tradition is good enough to perform in one season it would have been carried over to another. So the Wassail / Pace Egg song probably had the same root but became customised for the current season. Now, as to which came first it is anyones guess!

Cheers

DeG