Mysteresting
A hybrid of mysterious and interesting. Someone that is deeper than they let on, and tend to deflect their mysterious nature in an assortment of ways. Likely attended a very structured religious college in the deep south, that you will only find out after many years of friendship.
"Wow, Narlene sure is mysteresting. Did you know she went to Bob Jones? I would never have placed her there.. And to just find this out after 5 years of friendship??"