I have a younger cousin who started calling his grandpa "Honey" for some reason. It was really cute when he was small, but became somewhat awkward as the young man grew up. However, his Grandpa, Jim, was Honey until the day he died.
I wanted the little tyke to call me Judge LeGros but got overruled. So I picked my childhood nickname that hasn't been used by outsiders since I started school and the nuns insisted on no nicknames. So it's Jed for me and Mamere for the wife.
My daughter in law always called me Papa, that stuck with my granddaughter...the only one I can claim anyway. My wife is Granny, her family's tradition.
We wanted our grandchildren to be bilingual, officially, my wife is abuelita and I'm abuelito but those titles are difficult for really little children, so the adapted titles are "Ita" and "ito" the other grandparents are yaya and papu (Greek).
So far - with only two grandkids - we seem to be holding on Gram and Grandad. Moreover, I am blamed in the family for my maternal grandparents being stuck with Nanny and Boppy.
Our seven grand daughters and seven grandsons as well as our oldest great granddaughter all call us grandma and grandpa. Our youngest great granddaughter and our great grandson don't call us anything yet.
Grandson, 16, calls me grandpa. Granddaughter, 18, calls me by my first name. My ex-mother-in-law was determined to specify what my son called her. Okay, but I let the grandkids figure it out and am happy with whatever they decide.