The article is devoted to the study of the lexical inventory of the Old Church Slavonic language. The author proceeds from the idea of the lexical fund of the language as consisting not only of words but also phrases. The lexical inventory of the Old Church Slavonic language was created by the elite circle of literati in the process of translation (mainly from Byzantine Greek). Although the Old Church Slavonic language was based on the folk Slavic speech of the time, most of the Old Church Slavonic compounds and multi-word names were created by Slavic bookmen themselves. Many of these names appeared in the Old Church Slavonic lexicon due to the need to nominate concepts related to Christianity and “medieval encyclopedism”. The basis for the formation of these new names was the morphemic and phraseological calquing of Greek counterparts, which interacted with the mechanisms of nomination in the Slavic folk speech. The article demonstrates that the Old Church Slavonic nominations with multi-word names and compounds reveal “spheres of intersection”. As the author believes, these “spheres of intersection” were caused by the main and most difficult task that Slavic bookmen solved in translating both Greek compounds (or derivatives from compounds) and Greek multi-word names – the transfer of semantics of significant roots. Even within the epoch of the existence of the Old Church Slavonic language proper (i. e. 9th–11th centuries), there are variants of the translation of the same Greek compounds by both Old Church Slavonic multi-word names and Old Church Slavonic compounds. The occasionalisms that arose in the process of word-creation of bookmen in the form of compounds and multi-word names could subsequently be fixed in the usus of the language, but they could also remain hapax both within a certain text and within the entire corpus of Old Church Slavonic texts, which is not completely closed and has been studied extremely insufficiently.