It is derived from the Greek language, and means universal and complete. And as Christ told His Apostles to go and teach all nations all His doctrines, the word Catholic is reserved to that Church which alone teaches all Christ’s doctrines to all peoples—the Catholic Church. St. Ignatius of Antioch, about the year 110, first used the word to designate the true Church. He wrote, “Where the Bishop is, there is the Catholic Church.” Donatism broke away from the Church in the 4th century, just as Protestantism in the 16th, and St. Augustine declared that this heresy was cut off from the Catholic Church. In the same 4th century Pacian used the word Catholic as a mark of identification, saying, “Christian is my name, Catholic my surname.” He did not wish to be taken for one of those who protested against the Catholic Church, yet still continued to call themselves Christians.
Catholicity, Question 497 from Radio Replies Volume I Copyright © 1938 (by Rev. Dr. Leslie Rumble, M.S.C. and Rev. Charles Mortimer Carty).