There was an old Epiphany tradition in Europe, the “chalking of the door.”
On the 6th January (The Feast of the Epiphany – marking the visit to the infant Jesus by the Magi), friends and neighbours used to go to a particular house to pray the Magi’s and Christ’s own blessing upon it.
A prayer would be said, or a brief responsive liturgy recited.
Tradition has it that the Magi or Wise Men were called Caspar, Melchior and Balthazar.
The initials CMB are also an abbreviation of a house blessing in Latin, “Christus mansionem benedicat” meaning “May Christ bless this dwelling.”
The guests would then chalk on the lintel of the door to the dwelling these three letters, interspersed with crosses and flanked by the numbers of the present year.
Now, fancy that!