PARAN�, ARGENTINA.- As a boy, Blas Omar Jaime spent many afternoons learning about his ancestors. Over yerba mate and torta fritas, his mother, Ederlinda Miguelina Yel髇, passed along the knowledge she had stored in Chan�, a throaty language spoken by barely moving the lips or tongue.

The Chan� are an Indigenous people in Argentina and Uruguay whose lives were intertwined with the mighty Paran� River, the second longest in South America. They revered silence, considered birds their guardians and sang their babies lullabies: Utalá tapey-’é, uá utalá dioi — sleep little one; the sun has gone to sleep.

Miguelina Yel髇 urged her son to protect their stories by keeping them secret. So it was not until decades later, recently retired and seeking out people with whom he could chat, that he made a startling discovery: No one else seemed to speak Chan�. Scholars had long considered the language extinct.

“I said, ‘I exist. I am here,’” said Jaime, now 89, sitting in his sparse kitchen on the outskirts of Paran�, a midsize city in the Argentine province of Entre R韔s.

Those words kicked off a journey for Jaime, who has spent nearly two decades resurrecting Chan� and, in many ways, placing the Indigenous group back on the map. For UNESCO, whose mission includes the preservation of languages, he is a crucial vault of knowledge.

His painstaking work with a linguist has produced a dictionary of roughly 1,000 Chan� words. For people of Indigenous ancestry in Argentina, he is a beacon that has inspired many to connect with their history. And for Argentina, he is part of an important, if still fraught, reckoning over its history of colonization and Indigenous erasure.

“Language is what gives you identity,” Jaime said. “If someone doesn’t have their language, they’re not a people.”

Along the way, Jaime has had brushes of celebrity. The subject of several documentaries, he has delivered a TED Talk, lent his face and voice to a coffee brand and has appeared in an educational cartoon about the Chan�. Last year, a recording of him speaking Chan� echoed across downtown Buenos Aires as part of an artist project that sought to honor Argentina’s Indigenous history.

Now a passing of the guard is underway, to his daughter Evangelina Jaime, who has learned Chan� from her father and is teaching it to others. (How many Chan� remain in Argentina is unclear.)

“It’s generations and generations of silence,” said Evangelina Jaime, 46. “But we won’t be silent anymore.”

Archaeologists trace the presence of Chan� people back roughly 2,000 years in what is now the Argentine provinces of Buenos Aires, Santa Fe and Entre Rios, as well as parts of present-day Uruguay. The first European record of the Chan� was made in the 16th century by Spanish explorers.

They fished, lived a nomadic life and were skilled clay artisans. With colonization, the Chan� were displaced, their territory shrunk and their numbers dwindled as they assimilated into newly established Argentina, which launched military campaigns to eradicate Indigenous communities and open land for settlement.

Before Blas Jaime revealed his knowledge of Chan�, the last known record of the language was in 1815, when D醡aso Larra馻ga, a priest, met three older Chan� men in Uruguay and documented what he learned about the language in two notebooks. Only one of those books survived, containing 70 words.

The trove of information that Jaime obtained from his mother was far more expansive. Miguelina Yel髇 was an ad� oyend閚 — a “woman memory keeper” — someone who traditionally preserved the community’s knowledge.

According to Jaime, only women were Chan� memory keepers.

“This was a matriarchy,” said Evangelina Jaime. “Women were the ones who guided the Chan� people. But something happened — we’re not sure what — that made men take control again. And women agreed to cede that power in exchange for them being the only guardians of that history.”

Miguelina Yel髇 did not have any daughters to whom she could pass along her knowledge. (Her three daughters all died as children.) So she turned to Blas Jaime.

That is how he came to spend his afternoons soaking up stories of the Chan�, learning words that described their world: “atam�” means “river”; “vanat� be醖a” is “tree”; “tijuinem” means “god”; “yog黫n” is “fire.”

His mother warned him not to share what he knew with anyone. “From the time we were born, we hid our culture, because in those days, you were discriminated against for being aboriginal,” he said.

Decades passed. Jaime led a varied life, working as a delivery boy, in a publishing house, as a traveling jewelry salesman, in a government transportation department, as a cabdriver and as a Mormon preacher. When he was 71 and retired, he was invited to an Indigenous event and was nudged out into the crowd to tell his story.

Since then, Jaime has not stopped talking.

One of the first to publicize him was Daniel Tirso Fiorotto, a journalist who worked for La Naci髇, a national newspaper.

“I knew that this was a treasure,” said Fiorotto, who tracked Jaime down and published his first story in March 2005. “I left there amazed.”

After reading Fiorotto’s article, Pedro Viegas Barros, a linguist, also met with Jaime and found a man who clearly had fragments of a language, even if it had eroded with the lack of use.

The meeting marked the start of a yearslong collaboration. Viegas Barros wrote several papers on the process of trying to recover the language, and he and Jaime published a dictionary that included legends and Chan� rituals.

According to UNESCO, at least 40% of the world’s languages — or more than 2,600 — were under threat of disappearing in 2016 because they were spoken by a relatively small number of people, the latest year for which reliable data is available.

Referring to Jaime, Serena Heckler, a program specialist at the UNESCO regional office in Montevideo, Uruguay’s capital, said, “We are very aware of the importance of what he’s doing.”

While his work preserving Chan� is not the only case of a language once thought dead suddenly reappearing, it is exceptionally rare, Heckler said.

In Argentina, as in other countries in the Americas, Indigenous people endured systemic repression that contributed to the erosion or disappearance of their languages. In some cases, children were beaten in school for speaking a language other than Spanish, Heckler said.

Salvaging a language as rare as Chan� is difficult, she added.

“People have to be committed to making it part of their identity,” Heckler said. “These are completely different grammatical structures and new ways of thinking.”

That challenge resonates with Evangelina Jaime, who has had to overcome entrenched beliefs among the Chan�.

“It was passed down from generation to generation: Don’t cry. Don’t show yourself. Don’t laugh too loudly. Speak quietly. Don’t say anything to anyone,” she said.

For a time, that is how she also lived.

She shunned her ancestry as a teenager because she was bullied at school and scolded by teachers who doubted her when she said she was Chan�.

After her father started speaking publicly, she helped him organize language classes he offered at a local museum.

In the process, she began learning the language. Now she teaches Chan� online to students around the world; many are academics, though some say they have traces of Indigenous ancestry, with a small number believing they may be descendants of Chan�.

She plans to teach the language to her grown son so he can continue their family’s work.

Back at Blas Jaime’s kitchen table, the older man wrote his name out in the language he is trying to keep alive. It was a name that he says reflects the way he has lived. “Ag� Aco� In�,” which means “dog without an owner.” His daughter leaned in to make sure he spelled it correctly.

“She knows more than me now,” he said, laughing. “We won’t lose Chan�.”

This article originally appeared in The New York Times.