Christchurch was named by the Canterbury Association which settled the surrounding province of Canterbury. The name of Christchurch was agreed at the first meeting of the association 27 March 1848. It was suggested by John Robert Godley, who attended Christ Church in Oxford.
The usual maori name for Christchurch is Otautahi ("the place of Tautahi"). This was originally the name of a specific site by the Avon River near present day Kilmore Street and the Christchurch Central Fire Station. The site was a seasonal dwelling of Ngaio Tahu chief Te Potiki Tautahi, whose main home was Port Levy on Banks Peninsula. The Otautahi name was adopted in the 1930s. Prior to that the Ngai Tahu generally referred to the Christchurch area as Karaitiana, a transliteration of the English word Christian.
I had no idea of this early Maori name until yesterday when we visited an exhibition at COCA.