Everyone was non Maori before about 1850 i.e. no one called anyone a Maori in 1840.
At that time and so in the treaty as well, the word “maori” was an adjective meaning ordinary, that’s all.
Just read any copy of the actual treaty written in the native language and notice how although they use capitals for nouns, every time you see the word "maori" it has a small "m".It is an adjective.
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In the early days, Europeans called Maoris "New Zealanders" but once European settlement got under way and increasing numbers of settlers came to see themselves as New Zealanders, this would not have remained suitable so it would have been natural to call the brown-skins "Maoris" which they called themselves.
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The early polynesian settlers did not call themselves Maori until the arrival of Europeans in New Zealand. At this time they needed a name to mark their distinction from the new comers. The name Maori which means ordinary came into use.
http://maorisource.com/Maori.html
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The word maori
maori is an invented word used by the missionaries to describe the people who were included in the treaty of Waitangi and it was used to describe all people residing in this Land when the treaty was signed.
maori is an adjective which is a describing word and therefore does not require a capital/uppercase unlike a Noun which is naming word and has capital/uppercase.
maori is actually now a non-existent word which maori have adopted as being what they are and are not. Dont Google it as they the maori have complained and just recently the word ‘maori’ has been ‘red lined’ and given as a noun, if googled.
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How is the plural of the word maori written?
Some people simply do not add a plural suffix -s when the word maori is used in a plural context in written English, i.e., they use the word according to rules of maori language. It is interesting to see this usage appearing in New Zealand government publications and it may be become a feature of New Zealand English. Others follow style guides or publishing house rules which insist that the plural suffix -s be added when the word maori is used in plural context.
http://www.maorilanguage.info/mao_lang_faq.html
Below are links to images displaying the use of 's' in maoris
http://nzetc.victoria.ac.nz/tm/scholarly/tei-CowMaor-t1-body-d3.html
http://redmp3.cc/6130526/rotorua-maori-singers-eipo.html
http://tinypic.com/view.php?pic=16c9tub&s=9#.VsYGQ9Dtjcs
http://tinypic.com/view.php?pic=11ru4yg&s=9
http://tinypic.com/view.php?pic=34q8huc&s=9