 The festival is believed to have pre-Christian roots.After the Christianization of Ireland in the 5th century, some of these customs may have been retained in the Christian observance of All Hallows' Eve in that region—which continued to be called "Samhain"/"Calan Gaeaf"—blending the traditions of their ancestors with Christian ones.It was seen as a liminal time, when the spirits or fairies (the "Aos Sí"), and the souls of the dead, could more easily come into our world.