In earlier times the river that flowed from Tongariro Maunga (Mt Tongariro) across Taupō Moana to the sea was known as Waikato. Kainga (hamlets) existed along both sides of the river, with Waitahanui, the major pā of the local people situated at the delta. Te Hau o Tunono was a special wind that flowed with the course of the river, connecting the whakapapa (genealogy) shared by the people living along its banks.
Originally the river flowed westward to join the Tokaanu Stream near Maunganamu, but the actions of two Taniwha (water monsters) churned up the water, washed away islands and cut new channels, diverting the course. The new course from Poutu to the delta became known as the Tongariro River.