The accent originates with the immigration of gold miners to New Zealand in the 19th century gold rush. It is mainly an evolution of south-east English and Irish immigrants' accents.
It was also the first dialect to have its whole development recorded for researchers. The immigration of European settlers to New Zealand was around the same time that the tape recorder was invented and so a research in the 1940s happened to send a crew to interview immigrants on their experiences, these recordings showed the kiwi language’s development between different generations. People who were born in the 1850s-1860s shared their parents' accents, while people born from the 1870s to 80s had started to develop their own accent.
When the Kiwi accent was noticed in the late 19th century people thought it was because of laziness, and an unsuccessful speech training program was introduced both in school and through the media.
Kiwi has rising intonation and is spoken with a lowered velum, which gives it a very nasal sound. It also has a rising intonation similar to Australian.
The Alveolar approximate sound in kiwi is not pronounced unless it is before a vowel, for example the r in bored is not pronounced.
The glottal fricative is dropped in mid sentence pronouns. For example, the h in I told him to is not pronounced.
The alveolar lateral approximant becomes the back open-mid vowel so feel becomes fee-u.
Some vowels are pronounced as diphthongs, for example boot can be pronounced as boat and read as ruuh-eed and air as ear,
The open front vowel is pronounced as a closed front vowel so Pat is pronounced as pet and Allan becomes Ellan.
And the closed front vowel is opened slightly so pen becomes pin and Ellen becomes Iilan.
The closed front vowel can also be elongated. Dress becomes drees and best becomes beast.
Ellingham, V. (2019, September 10). A History Of New Zealand English: The Little Accent That Could. Babbel Magazine. https://www.babbel.com/en/magazine/history-of-new-zealand-english
New Zealand Accent - Phonetic Breakdown - The Voice Cafe. (2022, September 16). The Voice Cafe. https://www.thevoicecafe.net/learn-new-zealand-accent-phonetics-online/