Te Wai Pounamu is a Māori name for New Zealand's South Island which is also sometimes referred to as Te Waka a Maui (The canoe of Maui), from mythology.
Ngāi Tahu, the principal Māori iwi (tribe) of the southern region of New Zealand, utilised the very hard greenstone (jade) to make adzes and other implements, as well as ornaments. Particularly valued was a paler nephrite which the Māori called inanga, gathered in a remote area near what is now called the Dart Valley. Māori named the district wāhi pounamu, meaning "place of greenstone", and the South Island came to be called Te Wāhi Pounamu. This somehow evolved into Te Wai Pounamu which means "the water(s) of greenstone" but bears no relation to the original meaning.
The New Zealand Geographic Board has found that, along with the North Island, the South Island has no official name. The board intends to make South Island the island's official name, along with an alternative Māori name. Although several Māori names have been used, Maori Language Commissioner Erima Henare sees Te Wai Pounamu as the most likely choice.