May writes a plain m and is among the most stable consonants in the Semitic family. Its cognates are the Hebrew mem, the Syriac mim and the Arabic mim, and the correspondence needs no argument: the sound is the same in every branch, the name is recognisably the same word, and no sound change anywhere in the family has disturbed it. Beside the sibilants and the pharyngeals, which have shifted and merged differently in every language, m is a fixed point that the harder correspondences can be measured against.
May closes the group of four letters that give the Ge'ez order its traditional name. Ha, la, ha, ma read as a word is halehame, and the name works only because those four stand in that sequence, which is the South Semitic order rather than the abjad one. In Hebrew the same letter is thirteenth. Here it is fourth.
The Northwest Semitic name mem is the word for water, and the letter is understood acrophonically. Ge'ez may is close enough to be the same inherited name, but Ge'ez does not gloss it, and the atlas does not supply the Hebrew gloss on its behalf. Two things can be stated: that the letters descend from one ancestor, and that only one branch kept a meaning attached to it.