The article deals with motivation in the giving of unofficial names based on loanwords in the Upper Dniestrian area of Ukraine. Phonetic and lexical dialecticisms, often having certain phonetic or word-formation transformations, are the most common elements in naming practices. Loanwords comprise a significant layer of dialectal words; in particular, in southwestern dialects, these are primarily Polish and German lexemes. The motivation of some nicknames is unknown, which indicates that such proper names have lost their connections with appellatives. The subject of the study is the singling out of lexico-semantic groups of nicknames according to their motivational foundations, and investigating the loanwords origin. The study is based on the lexical material collected in settlements of Halych district, Ivano-Frankivsk region, representing the Upper Dniestrian subdialect of the southwestern dialect.