here we learn that its wassailing, not waffling, though they don’t explain further.
The practice has its roots in the middle ages as a reciprocal exchange between the feudal lords and their peasants as a form of recipient initiated charitable giving, to be distinguished from begging. This point is made in the song “Here We Come A-Wassailing”, when the wassailers inform the lord of the house that

“we are not daily beggars that beg from door to door but we are friendly neighbors whom you have seen before.”