My paternal g'parents were Grandma and Grandpa.
My mom's dad was Grandpa and his first wife was Granny (her choice to change it from Grandma later in life , and we didn't like the change, but we had to respect it). Second wife was Grandma Mayme.
My husband's parents were known as PopPop and Grandmom. His own g'parents were Poppy and Bushie (Polish nickname for grandmother) .
My parents are Pappaw (our son, their first grandchild, couldn't pronounce Grandpa so he said Pappaw and it stuck ) My mom chose to be called Ima ("ee-muh", Hebrew name for mother) .
We are not grandparents yet (praying, hoping) and I've spent a little too much time dreaming about what they'll call me.
I hope they DON"T do as my nieces did. They referred to their two grandmas as Cookie Grandma and Pretty Grandma.