potentialities

Truth be told, I didn't remember either, although as a wee Holmesian I had simply figured he was somehow connected to those Baskervilles and hence from Devon.

Now, I have just reread the entire book with this question firmly in mind, and didn't find the evidence particularly conclusive. Adso, in his initial description of William, says that he has freckles "such as I often saw among those born between Hibernia and Northumbria". However, William alternately answers to "Briton" and "Englishman" throughout, and also cheerfully cheerfully claims all the mad inhabitants of his isles as kindred in general, including a Hibernian poet whose work they peruse in the library. So.