It became known as the Catholic church within the first century...The inquisition was mankind's way of facing a threat which they could not comprehend....their religion, the ONLY Christian religion on Earth, which they knew to be the Holy church of Christ was under attack from a recently formed group of dissidents....they had seldom faced such opposition and thus acted accordingly....with complete and cruel and harsh retaliation.
These were not mild mannered protestors, they destroyed churches, libraries, monasteries, and were above and beyond any other evils that they had witnessed....they didn't know any other way to defend the church.
In the first Century, IIRC, the identifying phrase ‘Catholic church’ was actually catholic and Apostolic church’ and referred to all churches who believed that Jesus had come in the flesh, been crucified, died, and was buried. And the Third day God raised Him from the dead. The word ‘catholic’ did not refer to an institutional church until the 300s, established as such under Constantine’s leadership for making it a state religion. State approved and state directed.