https://samilhistory.com/2018/12/07/debunking-the-myth-that-the-british-invented-the-concentration-camp/

The actual term ‘concentration camp’ was invented by the Spanish (as campo de concentración or campo de reconcentración) in 1896 – three years before the 2nd Anglo-Boer War (1899 – 1904) started. It originated during The Cuban War of Independence (Guerra de Independencia cubana, 1895–98) was the last of three liberation wars that Cuba fought against Spain.

A rebellion had broken out in Cuba, then a Spanish colony in 1895. The rebels, outnumbered by Spanish government troops, turned to guerrilla warfare (and here another myth which says the Boer’s invented ‘guerrilla warfare’ is debunked).