Definitions for "Endpapers"
Paper, sometimes decoratively colored or marbled, that is pasted onto the inner covers, joining the book block to its boards and forming the first and last leaves of the book.
the leaves a binder adds to the front and end of a book to join the text block to the cover.
Or endsheets. These are the sheets of paper that form the bond between a book's binding and the book itself. One half of the sheet is pasted inside the cover and the other half remains free.