The king doth wake to-night and takes his rouse,
                  Keeps wassail, and the swaggering up-spring reels;
                  And, as he drains his draughts of Rhenish down,
                  The kettle-drum and trumpet thus bray out
                  The triumph of his pledge.

(Hamlet)

Wassao;"

A toast to health, usually at a festival; The beverage served during a wassail; Revelry; To toast, to drink to the health of another; To drink wassail
en.wiktionary.org/wiki/wassail