Actually the word comes from a fantasy series I recently discovered. The author, Brent Weeks, an American, spent some time in Carnarfon and included a number of Welsh place names in his novel. Some like Carnarvon were straight from Wales others, like Waeddryn and Llandarin, the Wy River etc. look Welsh-oid.
The authors has a forum and interacts with readers. When I pointed out the Welsh terms,he confirmed some and explained why he used them, but with 'Waeddryn: says, "The other word is indeed Waeddryn, and I'm not talking about that one.
Which I took as a challenge to figure out the word. Waed is also an Arabic word, a Saudi musician and an old Germanic word meaning "an item of clothing" http://en.wiktionary.org/wiki/w
So I may be way off base thing it is related to Welsh at all, even though the city is on the Wy River.