From Here We Come A-Wassailing:
We are not daily beggars
That beg from door to door;
But we are neighbors' children,
Whom you have seen before.
They are not beggars, but they would like a Christmas coin and a taste of Wassail as they go from door to door, singing.
"Old English wæs hæl, literally 'be you healthy.'" Here's an alcohol-free Wassail recipe but anything similar would work. In its classic form, it was made with ale or mead, and often nowadays with rum or vodka added to cheer up your guests.