Mayday

The Mayday callsign was originated in 1923 by Frederick Stanley Mockford (1897-1962).

A senior radio officer at Croydon Airport in London, Mockford 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. Since much of the traffic at the time was between Croydon and Le Bourget Airport in Paris, he proposed the word "Mayday" from the French m'aider.

The French word "m'aider" translates as "help me".

from alt.usage.english