The term “mayday” has nothing to do with the month of May
If you watch any sort of show involving planes or boats in distress, you're bound to hear this used.
The term “mayday” is used as a distress signal to indicate an emergency. It is used primarily by aviators and mariners. It comes from the French m'aider, meaning 'help me' and is used in much the same way as SOS.
The word came into existence after the 1923 Convention for Safety of Life at Sea Treaty was ratified by the United Kingdom and several other countries. The original wording of the treaty called for ships in distress to send out a wireless signal saying "SOS" — indicating a general call for help.
It was first used in 1923 by Frederick Stanley Mockford, a senior radio officer at Croydon Airport in London, who was asked to think of a word that would indicate distress and would easily be understood by all pilots and ground staff in an emergency.
Mockford was asked to think of a word that would indicate distress and could easily be understood by all pilots and ground staff in an emergency. The word he came up with: “mayday” from the French m’aider, meaning “come help me.” He reportedly chose the word because it sounded like the French pronunciation of “come help me.”
In 1928, an International Radiotelegraph Convention decided that May Day would be officially used as an international distress call in aviation.
On 1 January 1948, Mayday became the official call for help across the world.
Since then, it has been used to indicate any sort of emergency situation - not just in aviation - by thousands of people across many different industries around the world every year.