Folklorists excavate local customs that have persisted through the centuries to look for clues to the nature of the religious/mythological beliefs of people in the distant past. Many of these customs continue even today, though most have lost all real meaning except in providing a sense of community and kinship in towns and villages. Things like hunting the wren and the dancing of the Mari Llydd most certainly had meaning at some point in the distant past, meaning that can only be conjectured at this point.
The Mari Llydd is a Welsh custom of unknown origin. I used the imagery of the Mari Llydd in my novel “Three Wells of the Sea” when the townspeople of Caer Ys dress up their Mari Llydd with sea shells to represent the water horse. The traditional Mari Llydd is the skull of a horse placed on the end of a pole and decorated with ribbons, baubles, anything. It is carried by a man hidden in sackcloth and accompanied by a troupe of people who go door to door asking to be allowed entrance. They sing songs in exchange for food and drink, then move on. The keeper of the Mari offers to bestow good luck and fortune on those inside, though some have said they were threatened as children that if they were not good, the Mari Llydd, a ghostly horse, would come and carry them off. In this account, I see vestiges of the Puca, or Buca.
What is the significance of the horse among the various “Celtic” peoples? (The use of the term “Celt” is now hotly debated among scholars. There may have been no such thing, but a very loose collection of related tribes as different as the Romans from the Greeks.) More specifically, why the skull of the horse and its association with the winter solstice?
Winter solstice marks the day of the year when the sun reaches the southernmost declination. At dawn, it rises at the most southeastern point on the horizon and its zenith would be canted to the south. The effects of this is that the hours of night hit the maximum on this day, just as the hours of day hit a maximum on summer solstice, June 21. If you were an ancient person, you might wonder what makes the sun stop in its southern trajectory, do an about face, and start moving north again. The notion that the actions of humans might affect this turn is possible, the idea of appeasing the gods is one that is well documented in all ancient cultures.
My own feeling is that it has something to do with the reign of the two kings, the Holly King and the Oak King, made famous by Robert Graves in his book “The White Goddess.” Though his scholarship has lately been called into question, I feel there is evidence for the pagan origin of this lore in the hunting of the wren in Ireland. But to back up a little, the folktale of the Holly King and the Oak King says that two kings do battle for sovereignty over the land. During one half of the year, the Holly King reigns, and during the other, The Oak King reigns. The two solstices mark the battle of the kings, when one is slain and the other takes control and changes the path of the sun. There is some folklore that gives credence to it: Sir Gawain vs. the Green Knight, Lugh vs. Balor, etc. Neopagans have latched onto this myth and made it their own. All well and good, but let’s look at what might be considered evidence for such a story in Ireland.
Wren Day is celebrated on December 26th in parts of Ireland. The origin of the custom is unknown, though when taken with the idea of the duality of the year and the kings of light and dark, it makes some sense. The custom looks rather similar to the Mari Llydd, though instead of parading the head of a horse through town, the “Wren Boys” (wearing straw suits and motley) parade the corpse of a wren, a little bird known for singing sweetly even in the middle of winter. In distant times, the wren was actually hunted and killed, certainly a sacrifice. Nowadays, a stuffed bird is carried about. PETA would be proud. It is worth noting that the Irish refer to the wren as King of the Birds, and the Irish word for wren, dryw, is a cognate for the Irish word for druid. The king of the waxing year has been thought to be the robin, though not as much evidence can found for that idea.