endpaper(either of two folded sheets of paper used to connect the front and back covers of a book to the first and last pages) noun [UK: ˈend.peɪ.pə(r)] [US: ˈend.peɪ.pər]
flyleaf [flyleaves](blank page at the front or back of a book) noun [UK: ˈflaɪ.liːf] [US: ˈflaɪ.liːf]