I had two wonderful grandmothers. Mom's mother was Granny. Dad's mom was Grandma. Never had to wonder which one I was speaking about.
My husband's two oldest grandchildren, now in their 30's, have always called him Pancake. When first grandchild Kristi was about two she announced she had so many grandfathers - her dad's father, her dad's grandfather, her mother's father, her mother's stepfather, and even my dad got in there. My parents became Grandma and Grandpa Ted. Because we always took the family to IHOP when we visited them in Florida my husband became "the Pancake Grandpa" which quickly became Pancake. The other grandchildren call him Grandpa Jack (and me Grandma Verna) but to Kristi and Bobby it's Pancake to this day.