This book is ‘Display of Heraldry’ which was published in 1660.

Back then it was only the very rich who could afford books (the kind of people who had heraldry to display). It wasn’t uncommon for workers, even skilled ones to be illiterate. You can imagine this had to potential to cause problems when some of those skilled workers had the job of binding individual pages into a book.

To ensure the pages were stitched together in the right order a catchword was used. The last word at the end of a page would be repeated at the start of the next. This meant that even those who couldn’t read the text could match up these two words and avoid expensive errors.