Marion Healy’s great-grandfather Kwailu was just a boy when “recruiters” took him aboard a ship on a beach in the Solomon Islands. The destination was Australia, where, for meager wages, he would do backbreaking labor planting and cutting sugar cane for white farmers.

Thousands of South Pacific islanders like Kwailu were lured to Australian plantations in the 19th century, some through deception, others through force, and all through a colonialism that looted less-advantaged societies. So when Mrs. Healy recently heard Prime Minister Scott Morrison say that there had been “no slavery in Australia,” she wondered whether her people’s history, already little known, could be lost entirely.

“How dare you say that?” she said of the prime minister. “I’m a bit frightened that we might slip out of their memory.”

The Black Lives Matter movement, as it has swept the globe, has led Australia to look more deeply at entrenched discrimination against its Indigenous peoples and other minorities. Mr. Morrison’s remark, for which he later apologized, focused particular attention on outwardly racist policies in Australia’s past, a legacy many tend to overlook in a country that proclaims itself proudly multicultural.

Mrs. Healy and others descended from South Pacific laborers are often confused with Indigenous Australians, whose ancestors were the continent’s first inhabitants, and have faced similar discrimination. Though South Pacific laborers were not the only ones engaged in such work, the prime minister’s comment has created an opportunity for their descendants to cement a distinct identity.

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Some historians say that the more than 50,000 South Pacific islanders who worked largely on the sugar plantations of northeastern Australia from 1863 to 1904 were not technically enslaved because they were paid for their toil, albeit typically much less than white workers. Some laborers, including Kwailu, who returned to their home islands in the South Pacific ended up coming back to Australia.

“But there was kidnapping. Nobody would argue against that,” said Clive Moore, an emeritus professor at the University of Queensland who has extensively studied the history of the laborers, known in Australia as South Sea Islanders.