Wassail is one of the few drinks whose name descends from a greeting.

In both Old English and Old Norse, one way to say hello was to command the other person to be healthy: in Old English this was said “wes hāl,” and in Old Norse “ves heill.”

The “hāl” word becomes two words in Modern English “whole” and “hale,” as in “hale and hearty.” It’s also related to the word “health,” the state of being hale or whole.

By the 12th century, the custom had arisen in England to say this greeting when drinking, just as we say "cheers" today.

Judging from the fact that "wassail" ends in "-ail" (a later spelling of the Old Norse sound "-eill"), the word "wassail" probably comes from the Old Norse phrase rather than the Old English one.

Either way, the response was "drink hail," that is "drink healthy."

By 1300, the greeting said over the drink had become a name for the drink itself. Around the same time, it became a verb as well: "to wassail" meant "to have a good time saying (and drinking) wassail."

The term "wassailing" is also used for the custom of going from house to house asking for money or refreshments, similar to the practice of trick-or-treating. This is the usage we hear in the Christmas carol "Here we come a-wassailing":

We are not daily beggars

that beg from door to door;

but we are neighbours' children,

whom you have seen before.

So if you do decide to break out the libations this Christmas, you now have the perfect thing to say over your cup. Wassail!