SCORE. A thousand thanks to Kalara Zrinyi, who posted a link to a story on wassailing, which in turn contained a reference to a song allegedly sung by Harold Godwinson's men on the night before the Battle of Hastings. It referenced Cecil Sharp, who in turn referenced Wace.
Caveats:
- Written down by an Anglo-Norman
- At least 100 years after the Conquest
- In a document chronicling William of Normandy's righteous ascent to the throne
- Which is now lost, and all surviving copies would have been scribed by Frenchmen who would have no idea what they were looking at when they transcribed the Old English
I am willing to accept all those caveats!
Original, per Sharp:
Bublie creint e weissel
E laticome e drinchheil
Drinc hindrewart e drintome
Drinc helf e drinctome
He translates this as:
Rejoice and wassail
Let it [the bottle] come and drink health
Drink backwards and drink to me
Drink half and drink empty
I am suspicious that "drin to me" is "drink to me" and "drinc to me" is "drink empty," but it does make more sense that way.