The article is an attempt to compare results of some fundamental onomastic studies with some hypotheses. On the basis of an analysis of hydronyms Ch. Kraz concludes that in the territories which were once occupied by German, Celtic, Italian (with Venedian), Illyrian and Baltic tribes there exist the so called 'Old-European' hydronyms, common in form and the nature of their origin. W.P. Schmid calls attention to the fact that these old hydronyms, found in different parts of Europe, have almost as a rule equivalents in the Baltic areas. The Polish linguist Tadeusz Milewski divides archaic anthroponimic systems into two groups – the Eastern 'baga' and Western 'teuta'. To the 'teuta' group he classifies also German, Celtic, Illyrian and Baltic anthroponomical systems. Accordingly, what Milewski marks with the symbol 'teuta', is termed in Ch. Krauze's terminology as the Old European onomastic community. An analysis of onomastic material studied by the above mentioned scholars thus supports an argument confirming the hypothesis proposed by V. Pisani and J.W. Otkupshchikow. The Slavic languages have been shaped on the basis of dialects closely resembling the Baltic ones. A group of dialects that would become the Baltic dialects, situated in a periphery, might have completely fossilized and preserved many archaic features (= elements of 'old European' type). In the territories that would become the Slavic territories changes were more dynamic. A big role was played here by the Iranian element (= peculiarities of the 'baga' group).