Well, what I meant to say is they all
"Begin" with the letter "M".
I saw a similar riddle to this one. I would think the question would have been
"Whats in men and not in a lady?"
Logically, if this riddle was for kids, I do not think there is any "deep" meaning in the words but just the way it is arranged.
Is this how the "original" riddle was worded?? Otherwise, I don't have a clue to what the answer is.