Where is blackcough mentioned what book and page?

"Blackcough" is not a commonly recognized medical term or literary reference. It's possible you may be misremembering the term, or it could be a term specific to a particular fictional world or story.

To help me find the source, please provide more context:

* What type of book are you looking for? (e.g., fantasy, science fiction, medical textbook, etc.)

* Do you remember anything else about the book? (e.g., author, characters, plot details)

* Can you recall any other words or phrases used in connection with "blackcough"?

With more information, I can help you pinpoint the source of the term.