Plygain is the pre-dawn church service on Christmas morning in Wales, the last surviving remnant of the pre-Reformation Sarum rite. It was customary for many to spend the long night waiting for the service in the company of friends and family singing and celebrating. The service was lit by special plygain candles and consisted largely of singing carols. Plygain was originally a Catholic ceremony but survived in the Anglican tradition as a replacement of the Midnight Mass when Wales converted to Protestantism; it was kept alive in the nineteenth century by Methodist churches. In Carmarthenshire people paraded through the streets with torches on Christmas Eve before the service. Plygain gradually disappeared for a time from most areas because of the rowdiness of many of the participants who had spent their time waiting for the service by getting drunk but the tradition has been revived in many parts of the country.
The name seems to derive from the Latin pulli cantus or “cock crow song” which suggests that carol singing was long a part of the custom, or perhaps from a Welsh word for “bending”, as in prayer. A related observance which survives on the Isle of Man is the Oie’l Verrey.