Tendencies of formation of anthroponyms of rural residents in the oldest Lithuanian parish register of Joniškis dated 1599–1621

Parish registers are among the most important sources of Lithuanian historical anthroponymy. A chronologically unique baptismal register of Joniškis dating to 1599–1621, which is currently the oldest known Lithuanian parish register in Lithuania, stands out in the context of such registers. This article delved into the oldest inscriptions dated 1599–1600, which were found in the parish register of Joniškis, describes and analyses 290 personal names (second members of the binary naming model) in terms of formation. The following major research methods are used to discuss the data of historical anthroponymy: descriptive and comparative. The 290 analysed personal names were classified into two groups: anthroponyms with patronymic suffixes and anthroponyms without such suffixes. The first group was much larger. It comprised 274 (or 94.5 %) of all anthroponyms. The second group had 16 (5.5 %) personal names.