Word-formation motivation (WFM) is a fundamental and a key lexical phenomenon in the lexis of Slavonic languages. WFM is concerned with both appellatives and proper nouns. The study deals with a partial question of a proper name as a motivating element and provides with the factors affecting the onymic derivative capacity. In this respect, we refer to two theories: the theory of a proper name by V. Blanar and the theory of semantic structure of the Slovak deverbatives by K. Buzassyová. V. Blanar points out that onymic meaning consists of two parts, namely designation and reference. The fundamental Buzassyova's theoreme can be stated as follows: the derivative capacity of the verbal lexical units are determined by the intention of the verbal action. The present article points out that the derivative capacity of the proper names is determined by onymic meaning: the designation specifies basic derivatives of the word-formation paradigm of a respective proper noun (anthroponym, or toponym); the reference determines the number of other (non-basic) derivatives. The corpus of the proper names and their derivatives is taken from 'Slovnik korenovych morfém slovenciny' (Slovak dictionary of root morphemes, Sokolová et al., 2005).