I sympathize heavily with baby boomers who don't want to be called "Grandma" and "Grandpa". You're still young, baby boomers. And very spry. Those names do not befit you.
S-side grandparents: Mimi and Baba. Barbara says she might have liked to be Nana or something similar, but this was precluded by her sister Nancy's being Nancy, aka, Nan. As for Bob, he started answering to the name "Baba" when he went to China last year. Apparently the Chinese found the final consonantal "b" sound hard to manage. When he came home, and told Barb about it, she suggested that "Baba" would be a good grandparent name, especially since it might be the first thing Elliot would be able to say.
B-side grandparents: Nana (or Nanny) and Grandad. Nanny and Grandad were the names of my English grandparents, Peter's parents. I'm not sure just how they came about; they were settled on before I came on the scene, by my first cousin in England who is five years older than me. Peter has simply inherited the Grandad title -- or maybe we gave it to him. (Some are born to Grandad, some achieve Grandad, and some have Grandad thrust upon em.) Launa seems to be pushing for Nana instead of Nanny -- but it's not clear yet if that will stick. Everybody keeps saying "Nanny" by accident.
Nanny/Nana's mother (who, to me, is Grandma): we made her a Tshirt that said "Great-Grandma", but that seems so ponderous and impersonal to me now. Grandma's actual name is Juanna (the feminine form of Juan), and it occurred to me that this makes a fine title, too: Elliot, meet your Juanna.
So what does that make us? For the moment, Sarah is Mama. And I suppose I may end up as plain old Dad, but mostly so far we've been using a Welsh appellation that fell to hand (it was lying around partly because my own Nanny and Grandad lived in Wales for many years...): Da.
We'll post soon about Elliot's other great-grandparents . . . he has FOUR. (I think I had one.)