My in-laws' first grandkids called them Mimi and Poppy. Mimi I was okay with, but Lewis and I drew the line at Poppy (turns out he didn't much care for it either). So our kids call him Grandpa.
Natter 63: Life after PuppyCam
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We called our grandfathers "Grampa."
Grandpa for the win.
Both of our sets were Gramma and Grampa.
We called one Grandpa John and the other Grampy.
I don't know why I can barely hear it in my head! I go straight to Grampy, for whatever reason. FTR, my grandfathers: Gramps and Granddad. My Granddad was called Gramps by his other grandchildren.
Anybody else call their moms Momma?
In my close extended family, the following are used:
grandma/grandpa
grandmommy/granddaddy
grandma (last name)/grandpa (last name)
mom-o/dad-o
grandma/pa pa
grandma/granddad
meema/peepa
I called my mother Mama for a long time, but not Momma!
Oh, and my one little cousin called his great grandmother "Grammamommy" since she was his Gramma's Mommy.