Barack Obama is POTUS and Michelle Obama is FLOTUS, So What is Grandmom?

Just gave me a giggle on a rough day. How exactly would you pronounce that?

He's called POTUS, as in president of the United States. She's FLOTUS, for first lady. So what's the acronym for President Obama's live-in mother-in-law, Michelle's mom? Marian Robinson is FGOTUS: first grandmom of the United States.