Mari Lwyd - the Grey Mare - is the central character of a midwinter festive tradition celebrated in South Wales, and elsewhere. Through the dark nights between Christmas and New Year, the Mari leads her unruly retinue from house to house, winning access by outsinging the inhabitants at each door, and, once inside, boisterous revelries ensue.

There are many accounts of the Mari Lwyd tradition to be found in old newspapers. The interpretations of the custom found in them have just as many variations.

From the Evening Express, 28th December 1894 

MARI LWYD."

“Every native of Wales will have heard of “Mari Lwyd." The title is given to a horse's head decked with ribbons of all colours; eyes of glass, pricking ears, with a. sheet in the shape of a horse's body. Underneath that sheet is a youth, and he carries, bv means of two sticks fastened under the sheet to the lower jaw, lite head of the skeleton. By that contrivance the youth is able to open and shut the jaws of the skeleton's head, richly decorated. Another youth walks by the side of the figure with a garland-like bridle fastened to the jaws, and he is the guide.
Accompanying the “Mari Lwyd" is a “Pwn" (Punch) and “Siwen" (Judy). both with blackened faces, Punch carrying a formidable club, tand Judy a broom. I am tempted to confess - yes, I will confess it - that in my boyhood I have played the role of Punch in such a merry game of nights at Christmastide. How Punch joined the boys in singing:-

"Ma-e'n berllan o lydan nodau,
Llwvrfryd, hardd, a lifrau;
Rhilxtnau gwychion, brithion,
braf, au 'I A luniftvyd yn ddolenau."

She is a garden of richest flowers;
She is handsome. 0, the powers
Her ribbons gay, with rainbow sheen,
Are to be seen so glorious

I have simply endeavoured to convey the sentiments.

When the procession of the rural swains approach the farm-house or the village every door is instantly bolted against it.
Now for the explanation. “Mari Lwyd'" signifies Holy Mary, and implies the Virgin Mary, who is also named in Welsh bv "Wvryf Wen" or literally the White Virgin, but meaning Holy Mary. As in the Pen Rhys Monastery Poem (A.D. 1402):-

“Ef a rodd y Wyvy Fair Wen,
Wrth fesur araith Fosen;
Iesu yn ei bru, ar bren yn brynwr
A brenin Nef, bresen."

The whole affair is a fragment of one of the so-called Mystery Religious Plays of the Middle Ages, one of the methods adopted by good men to educate the unlettered masses.
It is evident that the horse now called “Mari Lwyd" carried a dramatic lady, representing the Virgin, towards Bethlehem-Judah. Bolting the doors against the “Mari Lwyd" represented the fact that there was “no room in the inn" for the Virgin, and that in consequence she had to rest in the cave (not stable - that is a wrong tianslation) of Bethlehem, where that night the Child-King - the Word made flesh - was born."