Many people have commented on the last name of the 304th Chancellor of Unseen University: Weatherwax, and asked if there is a connection with Granny Weatherwax.
In Lords and Ladies, Terry supplies the following piece of dialogue (on p. 224/161) between Granny and Archchancellor Ridcully as an answer:
“‘There was even a Weatherwax as Archchancellor, years ago,’ said Ridcully. ‘So I understand. Distant cousin. Never knew him,’ said Granny.”