A German ethnicity emerged in the course of the Middle Ages, ultimately as a result of the formation of the kingdom of Germany within East Francia and later the Holy Roman Empire, beginning in the 9th century. The process was gradual and lacked any clear definition, and the use of exonyms designating "the Germans" develops only during the High Middle Ages. The title of rex teutonicum "King of the Germans" is first used in the late 11th century, by the chancery of Pope Gregory VII, to describe the future Holy Roman Emperor of the German Nation Henry IV. Natively, the term ein diutscher ("a German") is used for the people of Germany from the 12th century.
When is the title of rex teutonicum first used? (If the question is unanswerable, say "unanswerable")
the late 11th century