Aha...that’s why I did not find it [Turkish]. This is actually mis-labeled, since this language had nothing whatsoever to do with the Turks, as this went on about 8,000 years before the present-day Turkish ethnic group got to Anatolia.
the English did the same in cornwall, Wales, Scotland and Ireland to a greater or lesser extent and the French did the same in southern France, Brittany etc.
Strangely enough in other places it didn't work -- as in the Bulgars, another Turkic people who became completely Slavicized.