I hypothesize that many of the nonsense syllables in early American folk songs came from a bowdlerization of Gaelic. These were transferred into the early minstrel shows and wound up in Appalachia. Since these ringle-dingle-tang-king-kong-kitchey-ki-mee-o's had no real meaning, they may have been a form of idioglossia although I doubt whether they were used as a language for communication.