I never got the chance to ask my mother that question. I know I caught her by surprise. She was supposed to be medically sterile due to a surgery at the time. My family never named anyone after a living person, so I wouldn't have been named for my father's mother. Thank goodness, Maud, ugh! My mother's mother passed away while my mother was carrying me, so a possible answer, despite the fact that none of my younger girl cousins was named for her, is Elizabeth. They called her Bessie, thank you, no. I wouldn't have minded Liz, Lizzy, Beth, Bess, or most of the other variants.
Then again, my name is gender neutral, which is why I kept it. Most likely I would still be Dion, perhaps spelled differently as they were in a rush to come up with a name for the unexpected surprise.
I did find out that the standard American pronunciation of my name, two syllables, is not how it's pronounced in Ireland. My name is the origin of the American name "Dean". Before I realized that I'm trans I toyed with adopting that pronunciation. When I change my name legally it will change from "Dion Patrick" to "Dione Patrice" and perhaps I'll pronounce the first name as "Deena".