Abstract: The subject of this research is the written historical sources that contain the term “Shaitan” and indicate the non-Orthodox nature of its origin in the history and culture of Finno-Ugric population of Ural and Siberia. Methodological framework is comprised of the Frontier Thesis by F. Turner. Historically, the traditional culture of Finno-Ugric peoples of Ural and Siberia was influenced by Muslim and Christian missionaries. Although in the XVII century, retained the influence of the Muslim – descendants of the Kazan and Siberian Khanates, it was also the influence of the Russian Orthodox Church. Such combination substantiated twofold processes in the history of Finno-Ugric peoples. The research employs the comparative-historical method that reveals the degree of Christian and Muslim influence upon the formation of the image of “Shaitan” and its use in the culture of Finno-Ugric peoples. The ehnographic materials collected and published prior to 1917 authored by N. Witsen, G. I. Novitsky, K. F. Karjalainen, and I. N. Smirnov served as the source base for this work. The use of the term “Shaitan” in Finno-Ugric cultures of Ural and Siberia has not been previously associated with the Muslim influence; this approach is implemented for the first time. The authors are also first to publish the field materials, which mention Num-Torum as the “former Muslim god”. The conclusion is made that relatively to the XVII century, there was no single (Christian) method of infiltration of the term “Shaitan” into local cultures, as for a long time, Finno-Ugric peoples of Ural and Western Siberia were under the influence of Muslims. The signs of such influence were replaced by Christianity throughout centuries, and the Islamic norms in the culture of Finno-Ugric peoples gradually faded away.