My brother (who has a different father then me) calls his greek grandmother ya-ya (that's probably not how to spell it).
And our American grandmother is grandma, gran'ma, gram, grams,or granny. Sometimes it's Moose but I forget why, some sort of inside joke I never learned. And on really rare occasions it's granny putt-bomber.. (said more like but) something about my mom drawing her a picture of a bomb (as a kid) that said "putt putt".
My grandma on my dad's side was dead Way before me, so I never got to call her anything.
My Italian friend calls her grandma Nonna.