Yeah, I called my maternal grandfather Pop, my children called my father Pop, and my great-grandfather was called, by his grandchildren and great-grandchildren,
Poppy Last Name. But when I once brought it up here in the context of this name, there were many who said they'd never heard of
Poppy as name for a grandfather, and few who said it was the name their grandfather had gone by.
But obviously "grandfather" is the first thing I think of too.