Kerching is the bright metallic ring an old shop till made when the drawer jumped open. People say it — often with a grin, sometimes with a little bite — to mean money is coming in. A British headline might go “Kerching!” the way an American one might go “Ka-ching!” It is informal, playful, and a bit cynical: it can mean “they're raking it in,” not always kindly. You will see it in papers and on social media more than in a careful essay. Though actually, the tills in shops now are quiet computers. The sound belongs to an older machine, but the joke stayed.