We were a little formal...
I knew three of my grandparents, who are all now long gone...
Grandmother Mary (my mother's Mother-never knew G-father on that side)
Grandmother Nellie (my father's Mother)
Bapa Harold (Nellie's husband, not my actual grandfather, she had been widowed and remarried, but he was the only one I knew).

Of course, to go with that, my mother was ALWAYS "Mother"-no nickname until I got older and wanted to antagonize her.