No, a rum dog is not a boozy sausage in a bun. In fact it is a steamed pudding originating from the Lake District, where the term 'dog' used to be slang for suet. The original version did not use egg or butter, but here, the addition makes the pudding lighter. I've also used a fruit loaf to make it more special. If are a vegetarian, or do not like using suet, then you can simply leave it out, and it will not affect the overall outcome.