When did Boxing Day become St Stephen's day in Ireland?

It is theorised that the Wren celebration has descended from Celtic mythology.[2] Ultimately, the origin may be a Samhain or midwinter sacrifice and/or celebration, as Celtic mythology considered the Wren a symbol of the past year (the European wren is known for its habit of singing even in mid-winter, and sometimes explicitly called "Winter Wren"); Celtic names of the Wren (draouennig, drean, dreathan, dryw etc.) also suggest an association with druidic rituals. The tradition may also have been influenced by Scandinavian settlers during the Viking invasions of the 8th-10th Centuries. Various associated legends exist, such as a Wren being responsible for betraying Irish soldiers who fought the Viking invaders by beating its wings on their shields, in the late first and early second millennia, and for betraying the Christian martyr Saint Stephen, after whom the day is named. This mythological association with treachery is a possible reason why the bird was hunted by Wrenboys on St. Stephen's Day, and/or why a pagan sacrificial tradition was continued in Christian times. Despite the abandonment of the wren killing practice, devoted Wrenboys continue to ensure that the Gaelic tradition of celebrating the Wren continues although it is no longer widespread.[3]

Similar traditions of hunting the Wren have been claimed to have been reported to have been performed on the Isle of Man on New Year's Day and in Pembrokeshire, Wales on Twelfth Day (6 January)[4] and, on the first Sunday of December in parts of Southern France, including Carcassonne. [5] The custom has been revived in Suffolk, by Pete Jennings and the Old Glory Molly Dancers and has been performed in the village of Middleton, every Boxing Day evening since 1994.[6]

In Galicia, Spain, "Caceria del rey Charlo" ("Chase of king Charles") was performed. The inhabitants of Vilanova de Lourenza would chase down a wren and, after tying it to a pole, would parade it and show it to the abbot of the local monastery, who would proceed then to offer them food and drink and appoint two leaders of local town council out of the four candidates proposed by the neighbours. This tradition has been recorded since the XVIth century.[7] The sources are somewhat misleading about the date, since they claim it was "New Year`s Day" but it might mean "The day after Christmas", which was regarded back then to signal the end of the year[8]