The only objective criterion that allows us to determine the cognitive aspects of ancient anthroponymy, in our opinion, can be the data of typological, areal and comparative analysis of all known anthroponymic systems of Indo-European languages. Therefore, the materials of the Baltic and Slavic ancient onemy in the work offered to the reader are presented against the background of the analysis of the proper names of a number of related languages. The presence of a large amount of factual material is a kind of mirror, reflecting the nature and reasons for the appearance and distribution of many proper names.