The article analyzes the existing hypotheses of the origin of the words pravoslavьny (Orthodox) and pravoslavie (Orthodoxy): 1) the erroneous perception of the second part of the composite ὀρθόδοξος (δόξα) as ‘gloryʼ instead of ‘faithʼ and 2) a change in the meaning of the noun pravoslovie (jurisprudence), which is a typical translation of δικαιολογία ‘defense in the courtʼ in accordance with ὀρθοδοξία ‘the traditional and universal doctrine of the Churchʼ with the subsequent mutual infl uence of morphemes slavand slov-. We consider all possible translations of Greek ὀρθόδοξος: pravy, pravověrьny, pravoslavьny, pravoslovьny, prostoslavьny. The paper analyzes how frequently these translations are used and when they fi rst appeared in the Old Russian language. The research is conducted using the material of Old Slavonic and Old Russian language dictionaries. By using quotes from sources that became available after the publication of the corresponding volumes of the dictionaries, dating of the occurrence of the words prostoslavets (Ilyin’s book of the 11th century) and pravy in the phrase pravaya vera (Sticherarion of the 12th century, Sofi isky prologue of the 12th/13th century) are made earlier. The paper also explains the origin of
the adjective prostoslavьny.