With the coming of Christianity the early Christian churches in Ireland sought to win converts by incorporating many of the old Celtic festivals, Christianising them in the process. Pope Boniface IV designated the 1st of November as “All Saints Day,” honoring saints and martyrs. He also decreed October 31 as “All Hallows Eve”, a feast day which eventually came to be known as Hallow’een.
Scholars today widely accept that the Pope was attempting to replace the earlier Celtic pagan festival with a church-sanctioned holiday. As this Christian holiday spread, the name evolved as well. Also called All-hallows Eve or All-hallowmas (from Middle English Alholowmesse meaning All Saints’ Day). 200 years later, in 1000 AD, the church made November 2 All Souls’ Day, a day to honor the dead. It is celebrated similarly to Samhain, with big bonfires, parades, and dressing up in costumes as saints, angels, and devils. Together, the three celebrations, the eve of All Saints’, All Saints’, and All Souls’ day, are called Hallowmas.