noun: used to define an overweight woman who is oblivious to her obesity.

Informal, friendly generic word used in place of a proper name like Buddy. Bubba as "Brother" is used especially by Southerners, Westerners and Black Americans (and small kids who can't say "brother") as a friendly or familial term thus Baby Bubba is the same only more so. Doesn't have the possible misunderstanding of disrespect of Bubba by someone who looks down on southerners.