> Maybe for the same reason the names of famous cities (especially if already famous in the past) are translated into foreign languages.
They're not translated as much as they are derived from the same etymons used by the languages spoken there. Italian Acquisgrana or French Aix-la-Chapelle derive from Latin Aquis {capella, grana, villa}. The only properly official name most cities had throughout Europe was in Latin rather than any vernacular, including in areas where non-Romance languages were spoken such as German, English, Polish and so on.
They're not translated as much as they are derived from the same etymons used by the languages spoken there. Italian Acquisgrana or French Aix-la-Chapelle derive from Latin Aquis {capella, grana, villa}. The only properly official name most cities had throughout Europe was in Latin rather than any vernacular, including in areas where non-Romance languages were spoken such as German, English, Polish and so on.