The Wassail is an ancient celebratory custom. The term comes from the Anglo-Saxon for 'good cheer' and refers to a midwinter custom intended to welcome in the new year. It often coincided with St Thomas's Day, 21st December, where the poor would go house to house a-Thomasing or a-gooding: collecting money, clothing or food.
Rather like modern carol singing, wassailers would go from house to house, often the largest ones, singing traditional songs on return for a liberal supply of beer, cider or pennies. This was collected in a bowl, kept by the King of the Wassailers. In some cases the bowl was used for this purpose for a hundred years or more.
A Warwickshire wassailing song was:
Wassail, wassail, all over the town,
Our bread it is white and our ale it is brown,
Our bowl it is made of a map-a-lin tree,
And with our wassailing bowl we drink unto thee.
Apple trees are also commonly wassailed in winter to ensure good health the coming year. In some areas it took place on Christmas Eve, others on Twelfth Night (6th January,) or 17th January, which corresponds to Twelfth Night before the calendar alteration in 1752, a fact which reveals the age of the custom.
This wassailing involved pouring cider into the roots (and drinking liberal quantities at the same time) and often placing cider-soaked toast in the branches while singing songs which varied according to area.
As the pagan customs died out, the wassail tradition was transferred to the Christmas season, and is likely the origin of carol singing which is still going strong today.