The phrase “Holy Orthodox Church” became extremely popular among the faithful shortly after the Holy 2nd Synod of the Ecumene that gathered in Constantinople in 381. The Holy Orthodox Church of our Lord Jesus Christ started referring to herself as being orthodox rather than just catholic since one of the reasons catholic was used in our Nicene-Constantinopolitan Creed was because all individual heresies up to that time were not actually completely universal in their location with regard to having Holy Temples, clergy, adherents, etc. As various heretics and/or schismatics referred to themselves as being catholic, we chose the word "orthodox" to distinguish ourselves from them.
Interesting. I've always wondered when the Eastern Church began referring to herself as the "Orthodox Church," i.e., began using "Orthodox" pronominally and not just adjectivally. I didn't realize that it began as early as the late fourth century. I was wondering if you could provide some patristic examples of this usage. Thanks.
The term "Catholic" appears to have achieved pronominal status sometime in the third century, both in the East and West. Thus St Cyril of Jerusalem
But since the word Ecclesia is applied to different things (as also it is written of the multitude in the theatre of the Ephesians, And when he had thus spoken, he dismissed the Assembly75 ), and since one might properly and truly say that there is a Church of evil doers, I mean the meetings of the heretics, the Marcionists and Manichees, and the rest, for this cause the Faith has securely delivered to thee now the Article, "And in one Holy Catholic Church;" that thou mayest avoid their wretched meetings, and ever abide with the Holy Church Catholic in which thou wast regenerated. And if ever thou art sojourning in cities, inquire not simply where the Lord's House is (for the other sects of the profane also attempt to call their own dens houses of the Lord), nor merely where the Church is, but where is the Catholic Church. For this is the peculiar name of this Holy Church, the mother of us all, which is the spouse of our Lord Jesus Christ, the Only-begotten Son of God (for it is written, As Christ also loved the Church and gave Himself for it76 , and all the rest,) and is a figure and copy of Jerusalem which is above, which is free, and the mother of us all77 ; which before was barren, but now has many children.
And for the West, St Pacian
But under the Apostles, you will say, no one was called Catholic. Be it thus. It shall have been so. Allow even that. When after the Apostles heresies had burst forth, and were striving under various names to tear piecemeal and divide the Dove and the Queen of God, did not the Apostolic people require a name of their own, whereby to mark the unity of the people that were uncorrupted, lest the error of some should rend limb by limb the undefiled virgin of God? Was it not seemly that the chief head should be distinguished by its own peculiar appellation? Suppose, this very day, I entered a populous city. When I had found Marcionites, Apollinarians, Cataphrygians, Novatians, and others of the kind who call themselves Christians, by what name should I recognise the congregation of my own people, unless it were named Catholic? Come tell me, who bestowed so many names on the other peoples? Why have so many cities, so many nations, each their own description? The man who asks the meaning of the Catholic Name, will he be ignorant himself of the cause of his own name if I shall enquire its origin? Whence was it delivered to me? Certainly that which has stood through so many ages was not borrowed from man. This name "Catholic" sounds not of Marcion, nor of Apelles, nor of Montanus, nor does it take heretics as its authors. ... And yet, my brother, be not troubled; Christian is my name, but Catholic my surname. The former gives me a name, the latter distinguishes me. By the one I am approved; by the other I am but marked.