She's now dead, but when she was alive I called her Nana, but often when I am talking about her to other people I say Gran. Why on earth is this in the religion section btw?
Maternal - Granny Paternal - Nana. Though this was highly objected to by my mother when I was first born (she wrote thankyou notes etc to 'Granny and Grandad', but they always wrote 'Nana and Grandy' and insisted that that was what they were going to be called) so it stuck. Though I quite like the fact that I don't know anybody else who calls their grandad 'Grandy'.
My other grandmother was Grandma *surname* for some reason. I never really saw her, I have only vague recollections of her and I didn't go to her funeral (my parents deemed me too young).
Well I only ever knew one of my grandmothers because the other died even before my dad met my mum. I used to call the one I knew 'Nonna' (meaning 'Granny' in Italian) because she thought it sounded less old than 'Granny'
We don't have any Italian roots, it's just that she preferred being called that