DD has Nanna, Nanny, Nanna *initial*, Nanna *initial*, Granddad, Granddad *initial*, Grandpa, Grandpop.
All names that her grandparents chose and we were happy with that. You run out of options with so many.
She calls her great grandparents what we do except with great in front. Or in one case where she says big nan and big granddad.