But I found this word:
exonym (n.) : a name given to a person or place by foreigners; a name used by people not native to the place of reference; a place name or a personal name used by foreigners instead of the native-language version used by its inhabitants.
Examples are Moscow (the English version of Moskva); Germany (Deutschland); Japan (Nippon); Vienna (Wien). It's also been fairly common with names - using a name that sounds similar but is different from a person's personal name, often because of linguistic differences and often to make assimilation easier. ie. Charles for Karl; Julia for Juanita, etc.
As a writer, this intrigues me. Like jargon, it represents a certain kind of "inside" knowledge.
I write for English readers. But if I were to set a story in Moscow, which name would I use? Would it lend authenticity to refer to Moskva or just confuse the reader? (It certainly confuses my spell checker.) Tom Clancy uses the exonyms for many Russian cities but sometimes a Russian character would use the native name. Does the time frame or historic setting make a difference? Brock and Boede Thoene also use exonyms in their historic series.
And the last question: are those writers' examples enough to draw a "rule-of-thumb" by?
Fortunately for me, my next story is set in a pond. Which the characters simply refer to as "home."