The article deals with the distribution of full and hypocoristic forms of some widely given Christian personal names in the Old Russian language of the 11th–15th centuries. We discuss the dichotomy between full and hypocoristic forms of the same names, according to the social status of the person: Vasilij (Vasil’ko, Vasil’), Mixail (Mixalko, Mixal), Georgij (Jurij, Djurdi, Gjurgij, etc.), Dmitrij (Dmitr). With the help of diachronic analysis, we track the general evolution in the field of Old Russian Christian naming. It was found that at the early stage Christian names appear only in their full version and with reference to saints and church figures, while lay persons normally carry original Slavic names. Subse-quently, Christian names began to be used more regularly in everyday life, first (from 11th to end 13th) in their hypocoristic form (-ko derivatives for princes and noble persons, truncated forms like Dmitr for people standing lower in the social hierarchy). At this stage Christian hypocorisms function primar-ily as adaptive means for borrowed names and hardly ever have any diminutive or affectional meaning. By the 14th century, hypocoristic forms (both-ko and truncated forms) eventually develop additional pragmatics associated with a lower social status. As a result, for those occupying a higher place in the social hierarchy, hypocorisms are gradually replaced by full forms. Further comparison of chronicles with birchbark letters confirmed the initial adaptive function of hypocorisms and helped establish the time frame of the “adaptive” stage of Christian hypocoristic forms usage more precisely. © 2021, Russian Academy of Sciences. All rights reserved.