What is the language used on food can? In season 2 episode 4, Reiner suspects Ymir.
While searching her, he found Ymir holding a can of canned food. When he took the food can, he was unable to read the content written on it, while Ymir could.
What is that language? and why was Reiner looking so afraid ?
This is a great question. However, as others mentioned, you do not want to know the answer by spoiling the anime. 

You will know after the new episode which will be released today (S02E06), thus please read this spoiler only after you have watched the newest episode.

The actual name of the language is not known yet, but we know where it comes from. I will leave you with a small teaser.


   Reiner was pretending not to know the language.