N|uu is one of South Africa’s oldest languages, and it is on the verge of extinction. But Katrina Esau is on a mission to preserve the endangered culture and language of the San People: an indigenous tribe that occupied the Northern Cape Province and is known as the first hunter-gatherers in the region.

The language is believed to have 112 distinct sounds and its main characteristic is clicks. It’s a language that has been passed down to generations orally. In 2013, UNESCO estimated that there were 7 N|uu speakers left.

Classified as critically endangered by Unesco, N|uu is one of three languages known to feature a “kiss-click” produced with both lips.

Growing up on a white-owned farm on the fringes of the Kalahari Desert in apartheid-era South Africa, Katrina Esau was forbidden by her employer to speak the language she had learnt from her mother. For half a century, the click-rich language N|uu, once spoken by the hunter-gatherers of the Northern Cape, today known as San or “bushmen”, was almost forgotten.

The muting of Esau’s community spread widely across the Afrikaans-speaking Northern Cape province, following centuries of extermination and assimilation of the San. For several decades it was thought that N|uu, like many of southern Africa’s original click languages, was extinct.

But in the late 90s, after the country had transitioned to majority rule, Elsie Vaalbooi, a N|uu speaker, appealed on local radio for other speakers to come forward. It emerged that there were around 20 ageing speakers of the language in the Northern Cape region.

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Within a few years, that number had dwindled drastically. Today, there is one known fluent speaker of N|uu – Esau, who is in her late eighties.

After decades of being banned from speaking the language of her forebears, Esau has dedicated the past two decades to teaching N|uu in an effort to preserve the San language and culture. Despite years of silence, she never lost her fluency. “I didn’t learn this language; I sucked it out of my mother’s breast,” she says in Lost Tongue, a film about N|uu made in 2016. “But I buried it at the back of my head.”

In a schoolroom at the front of her home in Upington, Esau teaches local children the original language of her homeland. Africa is the only continent with languages in which clicks are regular consonants. The single pipe after the “N” represents a dental click consonant which is produced with the tip of the tongue against the upper teeth. N|uu, now classified as critically endangered by Unesco, is one of just three languages known to feature a “kiss-click” produced with both lips.

To teach this extraordinarily rich language, Esau – who was never taught to read or write – uses song, play and images. It helps her pupils, aged from three to 19, learn basics such as greetings, body parts, animal names and short sentences.

In recent years, Esau’s mission has been assisted by academics Sheena Shah and Matthias Brenzinger. Together with community members, the three established a N|uu orthography – a set of conventions for writing a language – and created educational resources for Esau’s school.

Currently, N|uu is not the only language at risk of dying out in South Africa. Several communities are trying to revive languages such as Nama, which was a Khoisan language spoken by about 250 000 people in parts of South Africa, Botswana and Namibia. “When you look at the African languages, you learn that they help communicate different perspectives on life, relationships, spirituality, the earth, health, humanity,” Brezinger told BBC recently.

According to government officials, Esau teaches at a small school located at the front of her house in Rosedale, outside Upington in the Northern Cape.

The work and determination to save the language have not gone unnoticed. Esau was awarded one of South Africa’s highest honors: the Order of the Baobab to honor her efforts to preserve the language and culture.