Here is a continuation of what I have found regarding "Roman Catholic Church".
I have gone through the Councils of the first millenium, as well as other local councils, and was not able to find any reference to "Roman Catholic Church". While Pope Gregory does mention "Roman Church", the context is clear that he is discussing the apostolic see, because he also mentions the "Jerusalem Church" and the "Church at Constantinople". There are five apostolic sees, three of them are listed here. Antioch and Alexandria are the other two. But this is just a sub-division of heirarchy. These Churches are obviously united in faith.
After examing the Church writings, I went to the Oxford Dictionary. In the "Oxford English Dictionary", the highest existing authority upon questions of English philology, the following explanation is given under the heading "Roman Catholic".
The use of this composite term in place of the simple Roman, Romanist, or Romish; which had acquired an invidious sense, appears to have arisen in the early years of the seventeenth century. For conciliatory reasons it was employed in the negotiations connected with the Spanish Match (1618-1624) and appears in formal documents relating to this printed by Rushworth (I, 85-89). After that date it was generally adopted as a non-controversial term and has long been the recognized legal and official designation, though in ordinary use Catholic alone is very frequently employed. (New Oxford Dict., VIII, 766)
The Catholic Encyclopedia goes on to discuss the Anglican useage of the term in their invention of the "Branch" theory - Anglican, Roman, and the Eastern Orthodox are supposedly Apostolic (as per the term's use in the Nicean Creed). I won't bore you with the details of that discussion. But it appears that this is where the term began.
Really, the term "RCC" is an attempt to obscure history, separating the current Catholic Church from the Catholic Church mentioned by St. Ignatius of Antioch in 110 AD. It does not withstand even the slightest of scrutiny, as there is no other "Catholic Church" mentioned by the Church Fathers. NOWHERE is there mention of an opposing "Catholic Church" by the Fathers. It seems clear that there is only ONE Catholic Church. I spent about an hour and it is enough to disprove the idea that "RCC" came from Constantine. If anyone has an actual document that says otherwise, I would be interested in seeing it.
Regards