Mōdraniht erroneously translated as the night of the mother by the venerable Bede, would represent the true pagan feast celebrated on the occasion of the winter solstice (December 21) as reported in the book De temporum ratione of Bede.
Incipiebant autem annum ab octavo Calendarum Januariarum die, ubi nunc natale Domini celebramus. Et ipsam noctem nunc nobis sacrosanctam, tunc gentili vocabulo Modranicht, id est, matrum noctem appellabant: ob causam et suspicamur ceremoniarum, quas in ea pervigiles agebant.
began the year on January 8th [December 25], which celebrates the birth of the Lord. That very night, which we have so sacred, they used to call with the pagan term Modranecht, that is, “Mother’s night”, because (we suspect) the ceremonies were in his honor.