I had to look this up... I will admit it took me a long second to get it.
Exonym: geographical name for a place or group of people outside of a place... My niece lives in Jerusalem and people call her Yankee.
An endonym same thing but inside of a place... Here in America we call people that "wave" the confederate flag, drink, and spit tobacco a "redneck" ....
Now I be way off of my understanding but this game is open to Mae interpretation right...lol