Shakhmatov was also responsible for publication and pioneering studies of minor or derelict Slavic languages. His studies of Slavic etymology revolved around the idea of close contacts and influences between the ancient Slavs and Celts, a hypothesis that was subsequently discarded. In particular, Shakhmatov was convinced that Prekmurje Slovene, spoken in Prekmurje and the Slovene March, contains Celtic elements due to its front rounded vowels "ü" and "ö". In fact, Prekmurje Slovene is simply dialect of Slovene, and the sounds "ü" and "ö" are common in other dialects of Slovene, such as in Prlekija and some parts of Carinthia. Hungarian nationalists employed this theory of Shakhmatov against the Slovenes as part of magyarization of the Slovene March.