mysterious brown

Mysterious brown: something brown on your skin or clothing that could be chocolate from a previously eaten snack or it could be dirt, or it could be shit. You can't be sure that it is chocolate or you could lick it off, so you have to clean it.

Oh no, I just ate a kit kat bar and then pet the dog and now I found something brown on my arm. That is some mysterious brown. I'd better wash it off with soap and water.