Ireland marks Christmas in much the same way as many other nations around the world, but we have quite a few traditions and customs that are pretty specific to this island.

Ireland marks Christmas in much the same way as many other nations around the world, but we have quite a few traditions and customs that are pretty specific to this island.
Christmas in Ireland lasts from Christmas Eve until the Feast of the Epiphany on 6 January and it’s on 24 December that one of the traditions marks the beginning of the festive season.
For example, after sunset on Christmas Eve a tall candle is placed on the sill of the largest window in the home and lit as a sign of welcome for St Mary and St Joseph.
The feast of St Stephen, the first Christian martyr, is marked on 26 December and in Ireland is often referred to as Lá Fhéile Stiofáin or Lá an Dreoilín or Wren Day. Traditionally, this is also a popular day for visiting family members and going to the theatre to see a pantomime
The name alludes to several legends including ones found in Irish mythology that link the life of Jesus to the wren bird. In a fading tradition in all but a few parts of Ireland, people dress up in old clothes and straw garments and travel from door to door carrying fake wrens during which those taking part sing, dance and play music.
Dependent on which region of Ireland you are in those taking part are called either “wrenboys” or mummers. Mummers carry on the tradition at the village of New Inn, Co Galway and Dingle, Co Kerry. In the North, the tradition is still often observed in Co Fermanagh.
The tradition has its roots in ancient Ireland when a real wren was killed and carried around in a holly bush tied to a long pole – these days fake birds are used.
The wren is one of the smallest birds in Ireland, but it has a very loud song and is sometimes called the “king of all birds.”
This is because of the legend of a little wren who rode on the top of an eagle’s head and boasted he had “flown higher than an eagle.”
Wrens were hunted for many years throughout Europe in medieval times with Ireland no exception to that.
In most parts of the island, the tradition died out in the early 20th century and the rhyme often used during the procession was “The wren, the wren, the king of all birds. On St. Stephen’s Day was caught in the furze. Although he was little his honor was great. Jump up me, lads, and give us a treat.”
In past times, the captured wren was tied to the wrenboy leader’s staff or a net would be put on a pitchfork. It would be sometimes cruelly kept alive, as the popular mummers’ parade song states “A penny or tuppence would do it no harm.”
The song, of which there are many variations, asked for donations from the townspeople. One variation sung in Edmondstown, County Dublin ran as such: “If you haven’t a penny a halfpenny will do. If you haven’t a halfpenny, God bless you!”
Often the boys gave a feather from the bird to patrons for good luck. The money was used to host a dance or “Wren Ball” for the town on a night in January.

Source: The Wren Boy Procession and the Irish tradition of St Stephen’s Day – Derry Now