The article deals with the detailed research of the German microtoponymy of the Volga region. The toponym source is the doctoral thesis of a famous Russian linguist A. P. Dulzon, with a special chapter, where a list of 1049 geographical names of the Volga Germans is presented. The linguistic heritage of A. P. Dulzon, which addressed the studying of the Volga region German dialects, is unjustly forgotten and partly lost due to his being exiled to Siberia in 1941, where he was the head of the scientific school of studying native peoples’ dialects and toponymy. The toponymic material collected by A. P. Dulzon has not been thoroughly studied either by the scientist himself or by the following generations of linguists. The main aim of our research, which is based on new factual material and carried out in the field of sociolinguistics, is to define some unique features common for German microtoponymy, resulting from living for many years in multi-lingual surrounding. In this article the primary attention is given not only to the semantics and structure of toponyms, but also to the influence of the cross-cultural and cross-linguistic contacts. The research is focused on contact onomastics, the dynamics of cross-cultural interference, the problem of borrowings on the toponymic level, their adaptation in the language depending on the peculiarities of the German dialects of the language islands of the Volga region. It has been proved that borrowed Russian river names, geographical names, microtoponyms, and lexical units denoting Russian realia from the cultural and general sphere, were influenced by German island toponymy and underwent major grammatical and phonetical changes, becoming part of productive word-building models: composites and analytical structures. The research shows that the phenomenon of microtoponymy is characteristic for the German microtoponymy of the Volga region, which proved, together with various extra-linguistic factors, that the Germans led a secluded life on their confined territories. A conclusion is drawn that studying the island toponymy of the Volga Germans in the sociolinguistic aspect, i.e. taking into account all the social environments in which the language of this allochtonous community functioned, can be the foundation for the interdisciplinary investigation of toponymy established by A. P. Dulzon.