I've never liked the title, Grandma. So I knew when I had grandkids that I wanted to be called Nana. My grandchildren's other grandparents are also in town so she is Grandma, I am Nana. Her husband is Papa and mine is Nonny. His nickname was originally NOG - which stands for Nutty Old Grandpa, but they couldn't say NOG or Noggy so it came out Nonny and stuck.
NOG comes from my daughter when she was young. She was joking about growing up and having kids and them thinking her dad was theri Nutty Old Grandpa. So when she finally had kids years later, we brought it out of "storage." So with little kid modification, we are Nana and Nonny.