I got a few more suggestions for names of grandparents.

Marie Elena suggested Gram and Pop.
Mary reminded me of Omah and Opah... I shouldn't have forgotten that one, my nephew has an "Oma" and an "Opa"! Their family has a very German heritage, so that's no surprise, I guess.

Adriane also reminded me of Mimi, and they also had a Poppop... She also hinted at a fun story about my husabnd. In their family, they had a special name for her and my husband's paternal grandmother. If I get the story right... Hubby had a hard time with "Grammy" so he turned it into "Bambi." That one translated down the line; until her death last year, even her great-grandkids called her Bambi.

Am I missing any others?