Yuma Simpson (née Hickman), or Great Grandma Simpson was Homer's paternal grandmother from "The Old Country", which was most likely in Ireland, Scotland or Northwest England.
Yuma Hickman was born in the Old County, to Willard Hickman and Theodora Hutshing.
Yuma married Orville Simpson in the early 1900s.
While living in The Old Country, they had five children, Hubert, Abraham, Cyrus, Tyrone and Hortense.
The family emigrated to the USA around 1930 and for a few years, they lived inside the Statue of Liberty, along with their sons, until the head of it was filled with too much garbage.
While in the US, they has a sixth child, Chet, who is the youngest of Abe's siblings.
Later, the family would move to Springfield, North Tacoma, the town in which the show is set.
Although Yuma's death has never been mentioned, she presumably died before Bart