This happens to nail biters. The nail biter will be sitting around and chomping on their nails when they get a taste of something that was lodged under one of their nails. This strange substance remained safely stored under the nail unexposed to any hand washing. After careful backtracking to the point where this substance was acquired, the nail biter realizes that during their last trip to the crapper that finger had busted through the toilet paper and shit was lodged under that nail. Bon-apatite.
“Although the Coney Island down the street is disgusting, their carry-out is great!”