Last year, the Central Bank of Nigeria issued a new hundred-naira note to commemorate the union, in 1914, of the predominantly Muslim North and the predominantly Christian South. The redesigned bill includes a digital code that smartphone users can scan to see a timeline of currency used in the region, set against images of cowrie shells, which were used as currency in Nigeria before 1700, and manilla, a horseshoe-shaped metal bracelet that was historically adopted by Europeans to acquire slaves. These features of the new design were overshadowed, though, by an adjustment to the way the denomination was presented. On past banknotes, the words “Naira dari,” Hausa for “one hundred naira,” had appeared in Arabic script. Now, the Hausa was printed, like the Yoruba and Igbo, in small Roman letters, to the right of the larger centered text in English, the country’s official language. The change proved controversial.

The new bill, which was conceived under former President Goodluck Jonathan, an evangelical from the South, tapped into a deep historical divide and provoked strong reaction from Nigeria’s two major religious groups. Some Christians supported the move as a step toward de-Islamizing Nigeria, while many Muslims called it Islamophobic. Cletus Alu, a member of the Christian Association of Nigeria, in Abuja, told me that he would like to see the script removed from all of the country’s banknotes. “Nigeria is a secular nation,” he said. “It’s not good to give prominence to one religion or another.”

The country’s new president, Muhammadu Buhari, a Muslim from the North, has thus far stayed clear of the controversy. And so, this October 1st, on the eve of the fifty-fifth anniversary of Nigeria’s independence, the Lagos-based organization Muslim Rights Concern publicly demanded that the government reinstate the Arabic script. In a statement published on the group’s Web site, its director, Ishaq Akintola, described the change “as an act of hostility taken to spite Muslims” and claimed that some Christians had been “secretly agitating” for it. (Previously, the organization had accused Jonathan of replacing the Ajami with a symbol resembling the Star of David, in a bid to promote Zionism.)

On a drenched autumn evening, I met with Musa S. Muhammad, an archivist in his fifties, at a building in the Arewa House complex, beside the grand Sultan Bello Mosque in the northern city of Kaduna, to get a sense of the historical currents underlying the controversy. Arabic script, he told me, had been printed on nearly every note since the naira was introduced, in 1973, and on previous currency as well. To demonstrate, he instructed a colleague to remove a tenth-of-a-penny coin from a vivid twist of fabric. The piece was minted in 1945, under the British colonial regime, and three languages were stamped on its silvery face: King George VI’s name appeared in Latin, and the coin’s value was spelled out in both English and Hausa, with the latter spelled out in Arabic.

“This is politics between South and North,” Muhammad said, of the current dispute. He spoke with careful deliberation, his deep, raspy voice softened by a lisp. As he ran a finger over the Arabic script on a five-hundred-naira note sitting before him, the evening call to prayer rang out from the mosque, muffled by the rain. The letters on the currency, he said, are as secular in origin as the Roman alphabet used in modern Bibles. “Any non-Arab language written in Arabic script we call Ajami,” he said. “They feel that this is religious, but it’s not.” He leafed through the loose pages of an old manuscript written in Ajami, one of thousands that he is currently digitizing.

Muhammad is the chief archivist of Arewa House, which hosts a collection of thousands of manuscripts, some of them hundreds of years old. The national archives building, a short drive away, holds many more. Collectively, these manuscripts form a record of pre-colonial scholarship stretching from Timbuktu to Khartoum. Arabic script was first brought to Hausaland, as Muhammad calls his part of the North, by traders and itinerant scholars from across the Sahara, and was cemented by the establishment of the Sokoto caliphate in the North, long before Nigeria existed as a nation. He listed the indigenous languages that were first written down in Ajami: Hausa, which is spoken by more than thirty million people across West Africa; Fulfulde, which is spoken by the Fulani, nomadic herdsmen spread across the Sahel; Nupe, spoken by the Nupe people in Nigeria’s Middle Belt; and Yoruba, the language of Nigeria’s second-biggest ethnic group, which is religiously mixed and based mostly in the South.

Ajami later figured prominently in the North’s resistance to European colonialism. At the national archives, some of the earliest transliterations of Hausa Ajami into Roman script were completed by Major Frank Edgar, a British political service officer in northern Nigeria. They date at least as far back as 1911, and their paternalistic overtones are unmistakable. In the margins of “Litafi Na Tatsuniyoyi Na Hausa,” Edgar’s handwritten collection of his Hausa folklore and tales, the phrase “educated Hausas,” for instance, is crossed out with a line and replaced with “words by natives.” Still, despite efforts by the British to move toward Roman script, Muhammad told me, Ajami continued to be used to document everyday life: for tax documents, receipts, correspondence. He recited a few lines for me from a poem, written in Hausa Ajami circa 1917, which warned that Ankwai women from the central Plateau State were “very proud,” and would “chop” a man’s money.

The recent shift away from Ajami began in February, 2007, when the Nigerian government removed Arabic script from some lower-denomination notes; at the time, Mohammed Yusuf, the preacher who founded Boko Haram, had returned from Saudi Arabia and was growing his movement. The Central Bank released a statement that year saying that it had removed the Ajami in order to foster national unity, and to conform to Nigeria’s constitution, passed in 1999, which recognizes four languages for conducting government business, all of them written in Roman script. It also argued that Ajami was no longer necessary, because most Nigerians could now “easily read and write the Roman letters.” But Muhammad told me that millions of children in the North lack access to Western-style schools and can only read and write in Ajami. “How can we tell our children that we are knowledgeable people, that we are literate, if you remove this?” he asked.