My mum was Nannie and mother in law nanny, sounds the same so my mum became Nannie Oma. I got in early as I didn't want to be Nannie/y. I am grandma, surname begins with gr... so it trips off the tongue. I wouldn't mind granny or gran later, it still works with the surname.
It is confusing though when a stranger or even a friend refers to me as Nannie
To the children they look around for their paternal granny, who is nanny, and see me.
What with nanny, Nannie, nana, nana, granny, grandma, gran or even grand mama... there's plenty of choice.