The Angles and Saxons (ancestors of the modern English) came to Britain in the 6th Century. When they became Christians, they held a boar hunt to celebrate Christmas. This was probably a pagan Yule custom adapted to Christian use.
In due course the Boar's Head Ceremony developed. It was known in England from at least the Middle Ages. It migrated to the United States, where it is held today as part of the Madrigal Feast at Indiana University. It involves carrying in a boar's head on a platter. To accommodate demand, seven dinners have to be held. The Boar's Head itself is carried by madrigal singers. The Boar's Head Ceremony has been conducted at a number of other universities in the United States and Canada.
In England, the Boar's Head Ceremony continues to be held at Queen's College, Oxford. The platter on which the head is carried is fashioned of silver and was made in 1668.
The Boar's Head Carol is sung on this occasion. There have been several versions of this carol, but the most commonly sung one was first printed in 1521.
A Boar Loaf is consumed in Sweden at Christmas.