The author presents the history of a local language. In the 1750s, in Debrecen religious books were printed for the East Slovakian kalvinists living in the North-East part of the Kingdom of Hungary. These books were written in the East Slovakian dialect of the Zemplén county but in Hungarian orthography. This language had been used until 1923. In Slovakia, however, the adherents of the uniform literary Slovakian language, upon the initiative of the Slovakian kalvinist emigrants settled in the USA, gradually forced the East Slovakian kalvinist dialect out of the ecclesiastical use and in 1955 abolished it finally.