who named mayday?

Answer 1

You do mean the distress signal, right?

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

Mayday is an emergency code word used internationally as a distress signal in voice procedure radio communications, derived from the French m'aider. It is used to signal a life-threatening emergency by many groups, such as police forces, pilots, the fire brigade, and transportation organizations. The call is always given three times in a row ("Mayday Mayday Mayday") to prevent mistaking it for some similar-sounding phrase under noisy conditions, and to distinguish an actual mayday call from a message about a mayday call.

Answer 2

Mayday is an emergency code word used internationally as a distress signal in voice procedure radio communications, derived from the French m'aider.
The Mayday callsign was originated in 1923 by Frederick Stanley Mockford (1897-1962). Whilst 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.
FYI:
M'aider is the infinitive form of the reflexive verb "help me" within French syntax; however, it is not used as a stand-alone, imperative command in standard French.
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Answer 3

some French radio operator calling for help...Venez M'aider..(help me) all the other person heard was the last word and missunderstood it to be mayday