These are unique secrets, so take good care of them.

"Secret" refers to the classics collected in secret. For example:

The secret of this excavation is extremely precious.

"Fu" has two meanings, one is the book box. For example, "suitcase" means "suitcase", which often means "learning". Such as "learning from" and "going north". Another meaning is the same as "Ji" in the Secret Book, which refers to books. "Ji" in "The Secret Book" and "Gu Ji" refers to books.