The Mullogh runs aground on Cave Rock

Captain Joseph Thomas named this settlement Sumner, after Bishop John Bird Sumner, who was a leading member of the Canterbury Association. The area was surveyed and named in 1849 in honor of John Bird Sumner, who had just been appointed Archbishop of Canterbury and president of the Canterbury Association.

Sumner used to be its own borough, but it was later merged with the city of Christchurch as communication got better and it became less economical to operate small-town boroughs.

The Ngāi Tahu name for the beach between Cave Rock, or Tuawera, and Scarborough is Matuku Tako Tako. Both the state primary school and the city libraries here have used this name.

A. W. Reed gives the Māori name for this area as Ohikaparuparu, which means “place of rubbing, kindling, or planting” and “dirt, deeply laden, or a preparation of fermented cockles.” However, J. F. Menzies indicates that this name is connected to a settlement on the shores of the estuary between Redcliffs and Mt Pleasant. Menzies prefers to translate the name as "The place where sticks were rubbed together to make a fire with which to cook cockles in preparation for a journey." Andersen places this name on the beach at the mouth of the estuary, near Shag Rock, or Rapanui. James Cowan, retelling Sir Maui Pomare, suggests this name applies to the estuary shallows and means "fall in the mud."

Edward Jollie surveyed Sumner in 1849 for Captain Joseph Thomas, who was the advanced agent of the Canterbury Association. Jollie’s map from November 1849 showed 527 sections and many reserves, with provisions for churches, schools, cemeteries, a town hall, emigration barracks, and other town amenities. But his plans were abandoned because there wasn't enough money, and a new survey, which Sumner is based on, was carried out.