Baltic antroponymy is widely spread on the territory which was the part of the Grand Lithuanian Duchy, especially in its Ukrainian part. In the memorial edition of the 'Ukraine's Book of Memory' which sets the lists of Ukrainian soldiers that were killed in 1941-1945, there are regions (Zhytomyrs'ka- and Khmelnits'ka Oblast') with high occurence of Lithuanian surname 'Eismont'. Such zoning of the surname is interpreted as a result of migratory movement of impoverished Polish gentry in the 14th-16th centuries after Ukraine has become a part of Polish Commonwealth. Since 17th century, along with 'Eismont', the documents set the family of Esymontows'ky, Cossack gentry of Chernihiv. The duality of the Baltic name, functioning on the East-Slavonic basis, illustrates the opposition of presence/absence of the connective vowel -i- in disyllabic Lithuanian antroponyms (Eis-mont/ Es-i-montows'ky). The realization of this model is traced in Lithuanian-Byelorussian boundary. It is confirmed by M. Fasmer and 'Slownik geograficzny królestwa Polskiego': village Ejsymonty Wielikie/ Ejsmonty Wielikie (Bogorodyts'ka Volost' Grodnens'ky Povit), village Ejsymonty Malye/ Ejsmonty Malye (Maloberestovyts'ka Volost' Grodnens'ky Povit), village Ejsymonty / Ejsymonty Nadtobolskie (Vertslyashkivs'ka Volost' Grodnens'ky Povit).The given proper nouns are the evidence of the process of loss of the connective vowel -i- and subsequently, its disappearing. Furthermore, in word-formative context, the spatial modification of derivative structure of the proper name is traced. The family of Ejsymontows'ky had founded a village Symontowka. In the course of time, it has consequently come into the line of Ukrainian derivational suffix antroponymical oykomyms: Domontowka, Korbutowka, Montwidowka, Gedrimowka. Consequently, a peculiar 'corridor' of the proper name's spreading appeared. Furthermore, the way of 'coming' of the Baltic lexeme to Ukrainian language space is traced (probably, in the process of moving away from the Lithuanian boundary and the forms of Pluralia tantum. As a result, the origin decoding of Symontowka (and other antroponymical oykonyms) becomes easier (or more difficult?) because of the village proprietors - the family of Esymontowsky. .