A wayzgoose was at one time an entertainment given by a master printer to his workmen each year on or about St Bartholomew's Day (24 August). It marked the traditional end of summer and the start of the season of working by candlelight. Later, the word came to refer to an annual outing and dinner for the staff of a printing works or the printers on a newspaper.
The derivation of the term is doubtful. It may be a misspelling for "wasegoose", from wase, Middle English for "sheaf", thus meaning "sheaf" or "harvest goose", a bird eaten at harvest-time, cf. the "stubble-goose" mentioned by Chaucer in The Cook's Prologue.
The most likely origin is the word "Weg(s)huis", which was current in early Modern Dutch. This word (literally, "way house") was one of several words meaning the English "inn" and was figuratively used for "a banquet". The Low Country origin of the word "wayzgoose" has never seriously been disputed by etymologists, seeing that much early chapel terminology was borrowed from Low Country printers by their English apprentices (and later journeymen). The variety of spellings and pronunciations (including with and without the "z") indicate that it is an orally-borrowed Dutch word that fit somewhat uneasily in the mouth of English speakers.
Another plausible origin is a more general word for a merry-making or feast, reputedly referring to the grand goose-feast annually held at Waes, in Brabant, at Martinmas. However that is pronounced quite differently, as "Waas". It apparently means "cloud-veil" in Dutch: also there are no places called Waes or Waas in Brabant, but there are several places with "Waes" in their name in East Flanders.
Relations between England and the Low Countries were often very close, and it is plausible that such entertainments might have grown to be called colloquially a "Waes-Goose". It is not clear why the term should have survived later in the printing trade. Certainly the goose has long ago parted company with the printers' wayzgoose, which was usually held in July, though it had no fixed season. A keepsake was often printed to commemorate the occasion. It could be printed ahead of time, or the printing could form part of the evening's activities.