The present study describes ancient Permian settlement history in the light of onomastics. The principal aim of this onomastic survey is to determine the westernmost boundary of Permic hydronyms. A secondary aim is to distinguish different ancient Permian groups from one another, since the hydronyms suggest that there have possibly been four different kinds of Permian groups during the Middle Ages: Udmurt, Komi, northwestern (?Komi dialect) and Meščёra. To some extent, folklore, historical data and the history of different linguistic contacts have also been taken into account. The onomastic exploration has concentrated on the most usual Permic stems and Udmurt formants. In addition, the generic form -jug(a) has been examined.