In my few journal review, reviewers ask me to explain the nobility of the paper or unity of the paper, in some case both. In my research, my method is not new but first time introduced in my study region. Does it represent novelty or unity or both ?
I think the words you are referring to are "novelty" and "uniqueness".
The first one refers to the fact that the solution presented in your research is either new or pushes the boundary/performance with respect to other existing solutions. The second one refers to the possibility that your solution is not only novel but also "one of a kind", meaning you found out something nobody has thought of before.
I agree with Andrea de Giorgio 's interpretation. However, IF they did use the term "unity" it may also mean how your research fits into the existing body of knowledge on a topic. "Novelty" and "Uniqueness" may be more likely interchangeable, but for any new insights to add value you also need to show how they are connected to the previous studies and conclusions.