Perhaps as a witicism it could be suggested that he comes from the same planet as Gonzo, and are decended or evolved from the same creature. Sorry just a joke, the question I'd like to ask is how does it matter. There are probably a number of similar planets to his home world just as Kasshyk is similar to Endor which just had shorter inhabitants but similar dwellings. Perhaps Degobah is similar to his original home. Actually I'd imagine likely if he was happy to make a home for himself to go into hiding.
Can't remember which book but I remember reading that Yoda had hunted down and killed a powerful sith on Dagobah and thats what the tree is where Luke saw, and be-headed, the vision of Vader. The place being strong in the dark side made it an ideal place for yoda to hide as he couldn't be detected. I assume the place being dark and Yoda's inner light (can't think what else to call his "good force") simply cancelled each other out. Make sense?
Well that's how I understood his reason for living in such desirable surroundings.