The Maori name of the boulders is Te Kai - hinaki. According to the Maori folklore "the Kai" (food) hinaki (baskets) were washed ashore at Moeraki from the canoe Arai - uru, which was wrecked off the coast on a voyage south in search off the precious stone (Greenstone or Jade).
The Scientific Version
The Moeraki Boulders consist mainly of carbonate of lime, silica, alumina and peroxide of iron. Formed around a central core of lime crystals which appear to have the power of attracting and consolidating the above ingredients from the adjacent soil. The shape of the boulders is not due to the action of the sea. The boulders are 60 million years old.