A triple rendering of the word Mayday is the internationally recognized distress signal for an aeroplane in trouble. It is used by ships and others in the transport field as well, and also by fireman and the police. It is said three times to increase the chances of it being heard under noisy conditions, and lessen the chances it will be confused with some other kind of message.
The Mayday call sign was conceived by Frederick Stanley Mockford, a radio officer at England’s Croyden Airport, in 1923. At that time, a lot of air traffic was between Croydon and Le Bourget Airport in France, so when he was asked to find a word that would be easily recognized in an emergency, he decided to anglicize m’aidez (‘help me’)
Mayday was officially recognized as an emergency call in 1948.
Time Travelling With Kids 