Train horns have been a familiar railway sound for well over a century, signalling departure, warning people near tracks, and announcing a locomotive's approach. Online, the clean, isolated blast became a handy editing staple because it is instantly recognisable even without any picture of a train. Creators use it to mark arrivals, exaggerate fails, and punctuate jokes in short videos, streams and reaction clips. Its staying power comes from that simple association with something big, fast and unstoppable, which works across languages and needs no explanation.