[nekokami]

Originally Posted by montsnmags

Wikipedia says "the name is a pun on "hogwash", Hogmanay and Watch Night, and possibly on the ancient holiday of Samhain" though it doesn't cite a source.

Thanks. Through Google I found this interesting post from 1997 which is possibly an early source of this connection:
https://listserv.heanet.ie/cgi-bin/w...-L&D=0&P=46631

It seems possible that this comment came from or is related in some way to this segment (allegedly) of The Discworld Companion, by Terry Pratchett and Stephen Briggs:
http://www.geocities.com/liessa_nl/discworld
"Take Hogswatchnight, the Discworld winter festival. It's partly a pun on 'hogwash', but also takes in 'Hogmanay' and the old Christian 'Watch Night' service on 31 December. Even if people don't directly spot this, it subconciously inherits the feel of a midwinter festival."

That was the closest I came to finding a source attributable to Pratchett. Most of the pages were just copies of each other, usually taking text from the current Wikipedia article or what I suspect are just earlier versions of the Wikipedia article.