By the 1930s, the Bunuba population was reduced to a tenth of their size before invasion.
"In the greatness of our civilisation, spanning millennia, this was apocalyptic," Ms Oscar told the National Press Club on Wednesday.
Ms Oscar's term as Aboriginal and Torres Strait Islander Social Justice Commissioner - the first woman to hold the position - is coming to an end.
But her legacy will continue in the way she has amplified the voices of First Nations women and girls.
When Ms Oscar took on the role in 2017 she began travelling around the country, listening to Aboriginal and Torres Strait Islander women and girls for the Wiyi Yani U Thangani - which means 'women's voices' in Bunuba language - project.
The project will continue with the Wiyi Yani U Thangani Institute for First Nations Gender Justice, a dedicated research space at the Australian National University in Canberra, which the federal government announced on Wednesday would be supported with $3 million over four years.
She said it is thanks to the female line of her family and her grandmother, who turned her back on white society in the aftermath of decimation of the Bunuba.
"My grandmother lived in a corrugated iron one-room shack, just beyond the banks of the creek, where I slept, under the stars, on our Bunuba country with my mother and brother," Ms Oscar said, adding that while her mother worked as an indentured servant, her grandmother would take her walking on country and teach her Bunuba ways.
"These seemingly ordinary, everyday, acts by the matriarchs who raised me, were powerful forms of resistance against a colonial system that had attempted our eradication.
"A system that insisted this new Australia was not for us, and denigrated our women, implicitly condoning gendered violence, abuse and rape."
Ms Oscar's grandmother could not reconcile with Western society when she was alive.
"Our existences at the time were denied, emphasised by the fact that my father, a white station owner, never acknowledged me or my Indigenous siblings in his lifetime," she said.
Ms Oscar reflected that last year's referendum on a First Nations voice was a mirror on a moment, which she believes, despite the failure can still provide a wake-up call.
"The voice fell victim to what it aimed to counteract: mass discontent with socio- economic conditions which globally have given rise to sectarianism and populism, fuelling a surge in mis- and disinformation," she said.
"This burgeoning industry of lies and discriminations masquerading as truth and justice erodes our trust toward each other, government institutions and, for me, most significantly our ability to work together - the public with decision-makers - to weave, protect and sustain the social fabric."
In Bunuba culture Elders teach young ones to be "wanyjawurru", a giver, which Ms Oscar explained also encompasses the strands of the social fabric spoken of by women throughout Wiyi Yani U Thangani.
"Being wanyjawurru means we all have responsibilities to regenerate reciprocal relationships of care, safety, kindness and generosity," she said.
The Wiyi Yani U Thangani Institute will help foster dialogues of truth, Ms Oscar said.
"When we know each other, we can listen without fear, and act together with integrity and humility, walking into a future where we lay the foundations to account for everyone and exclude no one," she said.
Ms Oscar said her grandmother, like many women, gave her a vision for the future where women's voices were heard.
"I exist holding this vision, where I stand tall next to my grandmothers and mothers, our feet bare in the warm pindan soils of our country; gathered around us are our peoples and hundreds of other women and men with heritages from every part of the world, and there too are my non-indigenous brothers and sisters, their children and theirs and so on," she said.
"We all hold digging sticks and seeds, fires are lit, we sing, country hums.
"All is safe, all is well."
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