It is a blumpkin, a blow job given to a male while he is on the toilet, given by a relative. Being that it is a relative that is giving the oral sex which is considered redneck gives the term its beginning because country bumpkin is virtually synonymous with redneck.
Guy 1: Why do you look so happy?
Guy 2: My sister game me a blumpkin last night after she drank a bottle of Aristocrat.
Guy 1: Well at least with a Bumpkin Blumpkin you can't have a three-legged baby.
Guy 2: Well actually we still can but that's because we always fuck on Tuesday.