This is the darkest entry in the dictionary, and the one where the euphemism’s origin is clearest. “Cleansing” is the perpetrators’ word. It was how the people doing the killing described their own work, and the international press adopted it, in quotation marks at first and then without.

The phrase does two jobs. For those carrying it out, it makes murder a kind of hygiene. For those watching, it offers a category that is terrible enough to condemn but, crucially, is not “genocide,” a word that under international law obligates signatories to act. The United Nations itself notes that “ethnic cleansing” has no legal definition. That absence is the point.

Mamet’s theatre test is almost unbearable here. Put the phrase in a character’s mouth and the audience knows at once that the character is a monster or a coward. Off the stage, it was a headline for a decade.