George M Pruitt was the father of Luther Pruitt. I am positive his name was George since it was mentioned in both Luther's obituary and his death certificate.
George most likely died before 1880. Booker Pruitt is living with their cousin William Meador and the children on the 1880 census so I think it is unlikely that he is still alive at this point.
I don't know how much this will help but I think George Pruitt's mom may have been named Susie Lucas.
This might help. It lists Booker as the mother of Susan Pruitt Nichols. Not sure how Susie Lucas showed up on Luthers death record but I would keep notes on her as she may have been a first wife, maybe George remarried when Luther was really young??
"United States Census, 1920", database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:MH22-7BT : 1 February 2021), Susan Nichols, 1920.
Another one - Booker with son George
"United States Census, 1900," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M9WN-3DC : accessed 1 November 2021), Booker Pruitt, Magisterial District 5, Hudsonville, Custer Voting Precincts Custer village, Breckinridge, Kentucky, United States; citing enumeration district (ED) 10, sheet 16B, family 339, NARA microfilm publication T623 (Washington, D.C.: National Archives and Records Administration, 1972.); FHL microfilm 1,240,510.