  Please, be aware that the Celtic origin is one of several theories. At some point most of the modern Ukraine was part of the Khazar Empire and it is possible that title of khagan was a common custom of that time and place. The Eastern Europe went through so much transitions that to track down the real origin becomes close to impossible. About the reverts I am aware, but thanks for sharing that with me. The article about Ukraine in general came out well described although may be lacks some info and some might be skewed in a way. But the general picture is close to the real one.   