like H, M, U, Z F for January? Doesnt seem to make much sense, apart for Z for Dec and that they are at least in alphabetical order.
I would figure that the letters not being used for the months has something to do with them being used for something else. Like "W" could be mistaken for wheat?
Somebody said, "I ain't got nuthin'. Bill? Whatchu got?" And Bill says, just back from his eye exam, "Uhhhh, H, M, U, Z." And there writ history......