On a natural level, there are a variety of things that can cause shame. We might be ashamed of physical weakness or ugliness; we might be ashamed of a lack of education or a menial job; we might be ashamed of a dirty house or a misbehaving child. On a deeper level we would be ashamed to have people know our dark thoughts and unspoken desires. All of these have to do with our failings, our sense of not being good enough. And so it is in the Bible, where "shame" represents a knowledge and acknowledgement of our own evil, its hold on us and the delight we take in it.