This paper deals with establishing  motivational bases and semantical mechanisms for nominating medical terms. The lexical material for semantic and derivational analyses includes the terms from Posrbice od Orfelina do Vuka, Građa za rečnik stranih reči u predvukovskom periodu by Velimir Mihajlović and Terminološki rečnik srpske srednjovekovne medicine by Relja Katić. The aim of this analysis is to determine associative and analogical mechanisms that correspond to the language of the donor (Greek and Latin) and the recipient language. The lexical material was classified to microfields according to the principles by Nikita I. Tolstojs theory.