Meaning

noun an internationally recognized distress signal via radiotelephone (from the French m'aider)

originFrom the distress signal mayday, from French m'aider, short for Venez m'aider! (“Come to help me!”). The term was conceived in the early 1920s by Frederick Stanley Mockford, officer-in-charge of radio at Croydon Airport in England. He had been asked to think of a word that would indicate distress and would easily be understood by all pilots and ground staff in an emergency. Since much of the air…

Etymology from Wiktionary, CC BY-SA 3.0