Abstract: This study is devoted to the problem of the conceptual meaning, the definition of key-concepts. For this definition, we use the symbolic meaning of ancient runic inscriptions and analyze the meaning of the key-concept Os according to the Old English texts. The attention is drawn to the interconnection of two notions: “Os Drihten” and the transformation of the key-concept Os nuclear meaning at the edge of two epochs the Paganism and the Christianity. We can suppose that as a key concept, the concept Os has such important features as flexibility and stability. Despite the lack of practical material for a full conceptual analysis and at the same time the lopsidedness of this material, a runic script in our opinion, contains the basic elements of the key concepts of the ancient Germans. This allows to analyze not only in a synchronic timecut but also to trace the development of concepts qualities and features in a diachronic timecut especially during the transformation from an all-German Koine to individual national language systems.