The name "Porirua" is of Maori origin. It is possibly a variant of "Pari-rua" ("two tides"), a reference to the two arms of the Porirua Harbour. It was the name given in the 19th century to a land registration district that stretched from Kaiwharawhara (or "Kaiwarra") (on the north-west shore of Wellington Harbour) northwards to and around Porirua Harbour. A road climbing the hill from Kaiwharawhara towards Ngaio is still called "Old Porirua Road".