Mayday is the internationally recognised spoken distress signal used in radio communication by pilots, sailors and emergency services when a vehicle or vessel is in grave and imminent danger. The word itself is repeated, usually three times in a real call, to make sure it is not mistaken for another message. Online, a shortened two-word version has become a handy shorthand for disaster, appearing in gaming clips, reaction videos and memes whenever something goes badly wrong. Its familiarity is the reason it still works: listeners recognise the danger instantly, even without any context.