What did the Aztecs call their books?

The Aztecs didn't call their books by a specific word that translates directly to "book." Instead, they used the term "amatl" which referred to the paper itself, made from the bark of the fig tree.

These "amatl" were then folded and bound into codices, which is the term we use today to describe these ancient Mesoamerican books.

So, while there wasn't a specific word for the book itself, "amatl" referred to the material used to create them, and the term "codices" is used to describe the completed books.