The crime so total that it had no legal name until 1944, when the lawyer Raphael Lemkin coined the word for the deliberate attempt to destroy a whole people — a national, ethnic, racial, or religious group — and the 1948 UN Genocide Convention made it a crime under international law, defining it by specific acts done with intent to destroy a group, a definition argued over ever since: what counts, who decides, and why the promise to prevent it keeps failing.
Until 1944 the deliberate destruction of a whole people had no name in law. A Polish-Jewish lawyer named Raphael Lemkin gave it one. He fused the Greek genos, meaning a race or people, to the Latin -cide, meaning killing, and called it genocide. He had spent years arguing that the law punished the murder of one person but had no word for the murder of a people as such. While he campaigned, the Nazi state murdered most of his own family. Four years later the new United Nations made his word a crime, in a treaty whose signers swore that such horror would happen never again. The promise has been broken many times since. What counts as genocide, who gets to say so, and why prevention so often fails are the questions the word has carried ever since.