The word dude is a slang for man or boy. It is used a lot like Cool Dude. If a guy does something good, he is a cool dude. This is also used in the west like in Dude Ranch. A dude ranch is usually a ranch with horses and use to be run by mostly men. That would explain why the word dude became slang. Although, dude ranches are not solely run by men now. You will find women in charge as well.