From the 1928 Book of Knowledge.
From the Anglo-Saxon phrase Waes Haeil ('Be Healthy!'), wassailing is a very old custom in Great Britain. There are two basic forms of this toast or salutation: in one, groups go from door to door with a festive drink (usually spiced ale or wine and apples), sing happy wishes to the householders, and recieve some form of token payment in return. In the other, groups of men go out into the orchards and barns and salute the trees, splashing cider on the roots and placing apples or cider-soaked toast on the roots and branches, in hopes of an abundant new year.