Analogous to White Trash, but with a Southern orientation. A person classified as SoGarb could be someone with no college degree who drives a pickup, speaks with a southern accent, refers to people from the Northern US as "Yankees", eats a lot of fatty food, drinks a lot of cheap beer, and carries prejediced viewpoints.
Biily Joe from Alabama drives an old pickup with a confederate sticker on it. He likes getting drunk while watching NASCAR races. Billy Joe dropped out of high school, and speaks very poor English, carrying a strong southern accent and using words such as "y'all" or "aint". Billy Joe is Southern Garbage - or SoGarb.