It is strange to us, but often the aristocracy had a whole slang to itself, nearly unintelligible to outsiders. For example, the "Devonshire set" in the late years of George III/early Regency had its own slang, which included baby talk, extensive use of insider nicknames and mispronunciations (yellar for yellow and cow-cumber instead of cucumber, for example). It seems very strange to us to imagine these very refined people deliberately using wrong language (and it was quite deliberate) and we would surely cry foul if a book used nicknames such as Canis (dog) for a Duke, Hary-O for a lady or Poodle for a society man.