On non-uniqueness of solutions in historic-etymological research The author discusses the origin of the Ukrainian dialectal word копирдан (as found in J. Rieger’s A Lexical Atlas of the Hutsul Dialects of the Ukrainian Language, Warszawa 1996) hypothetically related to the Common Slavic *koprъ and its derivates denoting nettle. The problem of establishing this word’s origin illustrates some important issues in the theory and methodology of historical-etymological research caused by the genetic ambiguity of this entity. The ambiguity in question is connected, among other things, with the phenomenon of derivational polysemy, this phenomenon taking place when the same underlying stem (or its variants), or the same word-formative pattern employing this stem is interpreted differently due to the difference in extralinguistic derivational motivation reflecting different aspects and perceptions of the same object. The possibility of such plural motivation must be taken into consideration in semantic reconstruction, and the latter must anticipate, and allow for, cases of non-uniqueness of historic-etymological solutions caused by many-sidedness of analyzed linguistic entities as well as objects they denote rather than subjectivity of researchers.