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I have an Uncle Bubba. When I was little I had a hard time saying his name, when I would try to say it it sounded like "Bubba", so that's what he has been ever since.
Cool! I have a fourteen-months-older sister who couldn't pronounce "brother" when I was born. I've been Bubba to her and our Mama ever since. When Sister's first child, a girl, was born I was very surprised and very pleased when I walked into the room to see her for the first time and my sister said, "Your Uncle Bubba's here to see you." Until I became a family man and heard "Daddy" addressed to me, Uncle Bubba was the appellation I was proudest of.