Claxon comes from Klaxon, a brand of electromechanical horn first made in the early 1900s for early cars, bicycles and later submarines and factories. The name became generic in several languages, with claxon in French and Spanish simply meaning a car horn, and the harsh repeated blast became shorthand for warnings in film and cartoons. Online, the long recording spread on soundboards as an exaggerated alarm, reused whenever creators need a traffic, danger or wake up joke without any dialogue explaining the urgency at all.