The Holy Foreskin

Really:

Relics played an important role in medieval Christianity. The physical remains of saints and holy figures were considered an essential part of the faith, offering a powerful connection with Heaven.....
The most important relics were those associated with Jesus Christ – such as the True Cross where he died upon, or the mother’s milk of Mary. However, since Jesus was said to ascend to Heaven with his body, there could not be any of his own bodily remains left – except, perhaps, those that he left behind before he was killed, such as his blood or his finger nails.
All this brings us to the story of Jesus’ circumcision, which the Roman Catholic Church celebrated eight days after his birth on January 1st. Following the Jewish rite, Jesus was circumcised, which leaves the question of what became of his foreskin.
Very few articles have been written on the topic of the Holy Foreskin, partly because in the year 1900 the Roman Catholic Church threatened to excommunicate anyone who did so. However, Robert Palazzo bravely did his research and his article “The Veneration of the Sacred Foreskin(s) of Baby Jesus: A Documentary Analysis,” offers some interesting details about this relic. He notes that apocryphal gospels, such as the The First Gospel of Baby Jesus, which was written sometime before the 6th century, described how the foreskin was kept and passed down from generation to generation.
By the eleventh century, several churches in Europe explained they had the Holy Foreskin – the story often went something like this – Jesus’ mother Mary kept the foreskin, along with the umbilical cord, and later gave it to Mary Magdalene. We then jump forward several centuries to the time of Charlemagne, when an angel gave the relic to the Emperor. From there it went to this place or that place, including to Rome. In 1421, it was even sent to Cathernine of Valois in England, so that it would bring good fortune (and a pregnancy) to her marriage with Henry V.
Palazzo has been able to find at least 31 churches in Europe that claimed to have the Holy Foreskin sometime during the Middle Ages, including ones in Paris, Antwerp, Bologna, Compostela and Toulouse.
Meanwhile, one can also read a lot of theological commentary about whether or not the Holy Foreskin could be real, much of it negative.

Now that's a new one on me.  I knew that in the old days that New Year's Day was the feast of the Circumcision prior to it being changed to the feast of Mary, the Mother of God, but I'd never heard about the Holy Foreskin.