The distress signal “mayday” comes from the French phrase m’aider, meaning “help me.” Its sound was chosen because it could be understood clearly in spoken radio communication.
Frederick Stanley Mockford, a radio officer at Croydon Airport in England, proposed the word in the early 1920s. Much air traffic then crossed the English Channel between Croydon and Paris’s Le Bourget Airport, making a French-derived expression practical for pilots and ground staff on both sides.
The expression is a shortened phonetic form associated with “venez m’aider,” or “come help me.” Strictly speaking, French grammar would use “aidez-moi” as the standalone imperative for “help me,” but m’aider supplied the recognizable sound behind the English procedure word.
“Mayday” is used for a grave, life-threatening emergency in aviation and maritime radio. Standard procedure repeats it three times—“Mayday, Mayday, Mayday”—to distinguish the call from ordinary speech. SOS remains associated primarily with Morse-code distress signaling.