Similar to a Blumpkin, except that the girl is sitting on the toilet taking a poo or pee and giving oral to a guy that is standing up. It derives its name from the term chicken head, for the oral. Hen house refers to laying an egg, or taking a poo or pee. And Alabama... well if you put the name of a Southern State on something it just sound gross, but in a funny way.
Jenny gave Billy an Alabama Hen House last night, and I got it on film!