What is the coffin makers confession black book of secrets?

There is no known historical or fictional record of a "coffin maker's confession black book of secrets". It sounds like a phrase that might appear in a fictional story, perhaps a horror novel or a mystery.

It's possible that:

* The phrase is a fictional creation: The phrase might be used in a fictional work to suggest a dark and mysterious past, possibly hinting at secrets related to death, burial, or even something more sinister.

* The phrase is inspired by real folklore: Some cultures have folklore surrounding coffin makers or funeral practices. These might involve superstitions or beliefs that could be incorporated into a fictional "black book of secrets".

* The phrase is a misremembered title: It's possible you're misremembering the title of a specific book or story.

If you have any other context, like a specific book title, author, or a story you've heard, it might help pinpoint the source of the phrase.