Intrigued at the increasing usage of Aotearoa as a pre-European Maori word meaning (the North and South Islands of) New Zealand, recently I spent a few hours in the Christchurch library researching the topic. Oral tradition makes research of this nature never perfect, opens up many contentions but here’s my best effort.
Prior to European settlement there was no unified New Zealand, for want of a better term.
There were numerous Maori tribes, sub tribes in the North Island and South Islands, Stewart Island and Chathams.
There was, still remains geographic Maori names for all the islands, rivers, mountains which anyone can google up.
However it is fanciful, modern invention to suggest a 17th century Maori would have called his wider environment Aotearoa, encompassing all of what we now know as New Zealand.
A pre-European Maori living in say Southland mostly lived an isolated life, had little interaction with other tribes other than those bordering his village.
He or she would have no comprehension as to the scope of Aotearoa a united union of all Maori.
Few would have say called the South Island Te Waipounamu or other variants simply because they had no reason to think of the place other than it being the territory of ‘Tribe X’ or ‘Tribe Y’.
Even the word Aotearoa, the widely used native term for New Zealand’ is somewhat ambiguous as to its meaning.
'Ao' means world, globe, global, daytime and cloud.
'Tea' is white or clear.
'Roa' means long and slow.
Conceivably Kupe could have discovered his new homelands on a morning a large cloudbank parted and named the place Aotearoa for reasons other than them being shrouded in cloud (The Land of The Long White Cloud)
It’s all open to interpretation.
Aotearoa was therefore the traditional term for the North Island being the landing point of Kupe.
The most likely vernacular origins of the word Aotearoa we have adopted comes via English historians, commentators who made their own interpretations as to the lands being described to them to encompass the South Island.
Unless every book I read is wrong in reality there was no pre-European word for New Zealand as a whole as we know it today.
The traditional ‘myth’ of Kupe discovering Aotearoa is similarly varied to say the least, isolated to North Island tribes and then passed on-to South Island tribes via northern interaction.
There was/is no one unified Maori ‘discovery' or indeed 'creation' story which just further muddies the water.
In summary: Technically The South Island was never a part of what was loosely called Aotearoa or Kupe’s legendary discovery of what we now call New Zealand. For all intense and purposes Kupe never knew the South Island existed in the same fashion European explorers reported only what they found. As Maori populations expanded so did their legends e.g. Maui.