Too late, I've already confused them. Please explain the difference.
Novel works combine already existing concepts. Original works must be just that, original. They can not imitate in any way, shape, or form, that which has existed before. Thus it is impossible for the human mind to actually fathom an original idea. The human mind can only reshape that which already exists, it can not create original works, only novel ones.
For example, if I were to take a square and fashion six of them together, creating a cube, this would be a novel way to display squares (assuming my audience has never seen a cube). A cube is not my original work, I simply combined squares in a novel manner. We all stand on the shoulders of giants which are thus formed in a similar fashion to an ever increasing house of cards.