For years homosexuals were looked down upon. People derided them. However, Some homosexuals felt proud and positive about their sexual orientation, so they used "gay," which meant "blithe and happy," to denote themselves. Of course, folks who still disapproved of homosexuality resented the co-opting of this word. —I don't know that I understand the second part of your question. True, "dick" in slang means "penis," but sometimes people hear a word that can be understood in several ways in the way that is appropriate to its context. "Dick" is one of these words. "B itch," for instance, can be used as a derogatory, negative word for a woman, but it is also simply a female dog. If you were talking to a dog breeder, you probably would hear only the second, clinical meaning.