This name is more similar to Mariana or Marianna than Miriam (both forms of Maria) so wouldn't it make more sense to list it as a form of one of those than Miriam?
I just have to say that I hate this name. It's horrible and it's also my middle name. I guess my parents thought that I would love my name, but I hate it. And to you, who said it reminds Marijuana - well, you just made me hate this even more.