The song noded above by Segnbora-t was known to me as "Here We Come A-Wassailing" when I did my time in my high school's Madrigal chamber choir - most likely to distinguish it from the song below, I guess. This version is quite similar to the Gloucestershire Wassail, so near in fact that I had second thoughts about noding this version here. Still, this is the version that I learned and continue to sing for people when they ask me what my favorite Christmas carol is, and darn it, I can't find this exact version anywhere else on E2. The arrangement we sang was by Ralph Vaughan Williams, I believe. If you're looking for a live version, the Cambridge Singers and the New York Gay Men's Chorus do my favorite renditions by far.

Wassail, Wassail, all over the town,
Our bread it is white and ale it is brown;
Our bowl it is made of the green maple tree;
In the Wassail bowl we'll drink unto thee.

Here's a health to the ox and to his right eye,
Pray God send our master a good Christmas pie,
A good Christmas pie as e'er I did see.
In the Wassail bowl we'll drink unto thee.

Here's a health to the ox and to his right horn,
Pray God send our master a good crop of corn,
A good crop of corn as e'er I did see,
In the Wassail bowl we'll drink unto thee.

Here's a health to the ox and to his long tail,
Pray God send our master a good cask of ale,
A good cask of ale as e'er I did see,
In the Wassail bowl we'll drink unto thee.

Come, butler, come fill us a bowl of the best;
Then I pray that your soul in heaven may rest;
But if you do bring us a bowl of the small,
May the Devil take butler, bowl and all!

Then here's to the maid in the lily white smock,
Who tripp'd to the door and slipp'd back the lock;
Who tripp'd to the door and pull'd back the pin,
For to let these jolly Wassailers walk in.