Some believe that celebrating with a boar’s head is a holdover from a pagan tradition to honour Freyr, a Norse god of the harvest and fertility who was associated with boars. The Victorians used to make them out of cake which wasn’t quite the same.
The long and complicated recipe can be found in Charles Elmé Francatelli's The Royal English and Foreign Confectionery Book. (London: 1862), together with a fabulous picture of the finished result
