“Demonym”

You use them all the time, but you probably didn't realize they have a name. A "demonym" is the term given to a person from a specific locality — for example, city, state, or country. The word is derived from the Greek root "demos" meaning "the people" (as in "democracy" and "demographic") and the English suffix "onym" meaning "word, name."

I’m originally from Washington, D.C. That makes me a Washingtonian.
I work at Addis Creson. That makes me an Addis Cresonian.

In English, we use specific models to create demonyms, which makes them easy to invent (like “Cresonian” above). Here’s a handful of the stranger ones:

Monaco: Monagesque
Birmingham, England: Brummie
Brittany, France: Breton
Glasgow, Scotland: Glaswegian
Liverpool, England: Liverpudlian or Scouser
Newcastle, England: Novocastrian
Connecticut: Nutmegger
Sydney, Australia: Sydneysider
New Zealand: Kiwi
Massachusetts: Bay Stater
Indiana: Hoosier