“Foul matter” refers to the versions of a book that have been superseded by revised versions or by the final thing. Basically, once the book is finished, all previous versions are “foul matter.
Quite a term you’ve created there, Publishing Industry. I approve.
Here is the most recent “Foul matter” from the book I’ve been slaving over.
And because this post would not be complete without a pun on “foul,” here is a fowl matter.
In case you’ve ever wondered how Chicago pigeons keep warm.