I still think Wikipedia is a great reference website, even though most of my teachers kept strongly dissuaded me on making us of it. It can always be used as a starting point to find things. For example, my latest translation work deals with fictitious place names. How should I translate the French version of a place name like Urbia? What to call their residents? Urbians? That seems simple enough. Other place names might not be so easy.
Anyhow, looking up “Demonyms” on Wikipedia has given me a better idea on how to choose a proper sounding words. The term, obviously has nothing to do with “demons”, although some of the residents of these fictitious place names in the book I was working on, seem to have the typical traits of evil spirits. Demo- comes from the Greek word that means populace, and -nym simply means name.
The wiki page gives good examples, and I simply follow the pattern that’s nicely presented on their page. Examples of tricky place names are: Lilliput, Narnia and Oz. They even provide the example used in the Star Trek place name Qo’noS, where those war-loving Klingons apprently live, but that was simply up to the writer(s) to decide on.