This swirling pattern is digitally derived from marbled endpaper in an English commonplce book from circa 1652.
Commonplace books (or commonplaces) were a way to compile knowledge, usually by writing information into books. Such books were essentially scrapbooks filled with items of every kind: medical recipes, quotes, letters, poems, tables of weights and measures, proverbs, prayers, legal formulas. Commonplaces were used by readers, writers, students, and scholars as an aid for remembering useful concepts or facts they had learned. Each commonplace book was unique to its creator’s particular interests. They became significant in Early Modern Europe. (Wikipedia)