When my oldest granddaughter was born 17 years ago, my son and her mother asked me what my 'grandma name' would be. I liked Grammy, but that was my Mom. Nana reminded me of the dog in Peter Pan, so that was out. Didn't care for Grandma, or Granny, Grandmother was too formal, and so on. So I asked to have a few days to think about it.
I came back with two choices: "Oma" or "Gma" (GeeMa). (I didn't know that Oma was the German 'Grandma' at the time.)
MY son asked me how I came up with those choices. I told them that I was already used to both names - to which he responded "Well, Gee, Ma, ...."
I interrupted him by saying, "I rest my case." Everyone laughed and they made a decision.
They chose "Oma" and it really fits me. And I love being an Oma!
My husband is called "Pop-Pop", and occasionally, "Double Pop". It works for him.