Doesn't really have to describe anything internal or external based on my experience. A way for somebody to describe themself as rougher/tougher than they actually are.
He never saw the roughnessthat the girl calling herself the diamond in the rough was describing in her title for herself.
Nobody really thought there was any roughness to the girl that called herself a diamond in the rough but herself, everybody else just thought she was a bully who was silly more often than not.
1. Person - When a person has some hidden talent or characteristic or personality trait that is not immediate seen. But once you learn more about this person you see how much they are really worth.
2. Thing - Something that does not seem to be worth paying attention to but has a hidden quality that is not immediately seen.
Person- GUY 1 - "Man that girl is 350 lbs but is an expert pole dancer" GUY 2 - "Yeah shes diamonds in the rough"
Thing- GUY 1 - "Man this game is so old it's from 1981 who would want to play this" GUY 2 - "Yeah but man this is the originalDonkey Kong it's priceless".