Short answers, pulled from the story.
An endonym is the name a group, community, or place uses for itself from within, while an exonym is a name applied from outside by speakers of a different language. Deutschland is the endonym for the country English speakers call Germany.
Marcel Aurousseau, an Australian geographer, first used the term exonym in his 1957 work The Rendering of Geographical Names. James Matisoff later introduced the related term autonym into linguistics.
A substantial proportion of English-language exonyms for places in continental Europe were borrowed or adapted from French, including Belgrade, Bucharest, Cologne, Florence, Milan, Munich, Naples, Prague, Rome, and Seville.
Apache most likely derives from a Zuni word meaning enemy, Sioux from a Proto-Algonquian term meaning foreign-speaking, and Comanche from the Ute word kimantsi meaning enemy or stranger. Anasazi is a Navajo word meaning ancient enemies; contemporary Puebloans prefer Ancestral Puebloan.
Among the examples: Reza Shah requested the use of Iran over Persia in 1935; Cote d'Ivoire made its French name the official English designation in 1985; Turkey issued an order in December 2021 mandating Turkiye in official communications; and India changed Bombay to Mumbai in November 1995.
After China declared Hanyu Pinyin the standard romanisation in 1979, Beijing, Qingdao, and Guangdong replaced older English forms in most formal contexts. Older exonyms like Peking and Canton survived in fixed compounds such as Peking duck and Canton trade.