As a language learner, there always things to know~~

 

While it is a possibility that this expression comes from the French "M'aidez", it seems unlikely given that "aidez-moi" (help me) would be closer to the meaning of "mayday". "m'aidez" is not a command, rather it is the verb "help" and the object "me" with no subject. It would be "[you] help me", however, in French unlike English it is not customary to leave out subjects. In addition, an English speaker saying "help me" would clearly be using the command form, even though it is identical to the 1st person form. Also, it is more likely that a Frenchman would say something like "au secours" rather than a direct translation of the English expression "help me."

The international distress signal, used by ships and aircraft, comes from the French word "m'aidez".