The article describes grammatical peculiarities of individual nicknames in the Upper Dniestrian area of Ivano-Frankivsk region. An important characteristic of nicknames is the part of speech they are derived from. Although such unofficial anthroponyms have grammatical features of substantives, they may be derived from nouns, adjectives, verbs, or other parts of speech. Attention is drawn to lexico-grammatical categories, grammatical forms of nouns, substantiated adjectives, and other parts of speech that can be converted into unofficial names. Anthroponyms that correlate with first declension nouns and, less often, with second declension nouns may belong to both females and males, and preserve the corresponding declension paradigm. The plural form is most often used for forming family and lineage names that can later be used in the singular. Nicknames derived from adjectives indicate the gender of the named persons by their endings. Nicknames derived from verbs, numerals, particles, adverbs, and exclamations are less common.