The New-Zealand expression wahine toa (plural forms: wahine toa, wahine toas) designates a brave Māori female warrior, and, by extension, any strong or brave woman.

This expression occurs, for example, in the following from Dedications, in Quality of Life: A Phenomenological study of the experiences of Samoans with a disability in Auckland, Aotearoa New Zealand, by Nite Fuamatu, a thesis submitted in January 2019 for the degree of Doctor of Philosophy, Faculty of Education, Monash University (Melbourne, Victoria, Australia):

Sincere thanks to wahine toa, Auriole Ruka and Recenia Kaka, for their courage and dedication to promoting the well-being of Pasefika persons with a disability and the huge opportunity to be part of this and the wider whanau.

The expression wahine toa is from:
– Māori wahine, designating a Māori woman or wife;
– Māori toa, designating a Māori male warrior, especially one known for bravery and success in battle.

The earliest occurrence of the expression wahine toa that I have found is from the following obituary, published in Te Waka Maori o Niu Tirani (Wellington, New Zealand) of Wednesday 29^th October 1873:

HE TANGATA MATE.

Ko Mere Parari no Ngatihaunui. No te 5 o nga ra o Oketopa i mate ai ki Whanganui. He wahine toa ki te riri, toa taua i nga riri a te Kawanatanga ki te Hau Hau.
Mere Parari, alias Bloody Mary, of Ngatihaunui hapu, at Whanganui, on the 5^th instant. She was a desperate female warrior, and a regular Amazon in many a skirmish in the Government wars against the Hau Haus.

The earliest English uses of wahine toa that I have found are from stories by the New-Zealand author James Cowan (1870-1943):

1-: From Maori Heroines. “He Wahine Toa.”, written for The Otago Witness, published in The Otago Witness (Dunedin, New Zealand) of Wednesday 22^nd October 1902:

In Ahumai I recognise a truly heroic spirit, a woman who could face death without flinching, and defy all in order to save the life of one of her enemies, simply because he was friendless and no arm was stretched out to rescue. Long may brave Ahumai live to draw her little pension; and when she passes to the gates of the Reinga, may this pakeha scribe be alive to pen a last tangi to the memory of the heroine of Orakau. She is what the Maoris—slow as they are to compliment their womenfolk—delight to call a “wahine toa,” a woman truly valiant.
Instances of Maori women’s heroism in other quarters than the old-time battlefields are not wanting. […]
[…]
Here, too, up Hauraki way, we have a Maori heroine, a wiry old lady named Rahuite Kiri, who once distinguished herself in an even more perilous marine adventure than that fine swim by Julia Martin.
Rahui’s husband, Tenetahi, a well-known Maori mariner and scow-owner on the Auckland coast, was sailing merrily along one day in his crack cutter, the Rangatira, past the rocky shores of the Great Barrier Island, when a sudden, fierce squall tore down on them, and struck the cutter with irresistible force, and before Tene could let go the halliards the vessel capsized and sank. Tene and his wife, who was with him in the capacity of sailorman, were left swimming for their lives. For hours—how many they could never tell—they were in the water, vainly endeavouring to reach the island, before they were picked up. Tene, a strong, burly fellow, became so exhausted that he gave up, and that would have been the last of him had it not been for the pluck and endurance of Rahui. She supported her husband, floating and swimming, until she too was almost drowning, worn out by the superhuman task. Rescue came just in the very nick of time.
Neither Tene nor Rahui talk much about that day when both so nearly made food for the barracouta and the shark that haunt the Barrier coasts. But old Tene’s eyes shone with a rather unwonted, tender light, tough sea-dog as he was, on one particular occasion when I spoke of it; and looking across at Rahui, the blue-tattooed descendant of a long line of great-hearted rangatiras and chieftainesses, he said, in the quaint English that was one of his characteristics:
“Ah, my ol’ woman, he stick to me like what you call t’e brick, ne? He t’e good ol’ woman, te wahine toa!”

2-: From Coastwise Cruises. No II: The Mate of the Ariki Cutter, published in The Auckland Star (Auckland, New Zealand) of Saturday 12^th July 1913:

Paratene had a tough hold upon life, for he soon recovered. As for his good old wife, she was able to fill her pipe again and enjoy a comfortable smoke in a very little while. And Paratene was not backward in giving her her full due of praise. “Ah,” he used to say in after days, when he told the story of that black night in the Gulf, “she te bes’ ole woman in te world! She stick to me like what you call te brick. Ne ra! She te prave wahine, te wahine toa!”