A catchword is a word placed at the foot of a handwritten or printed page that is meant to be bound along with other pages in a book. The word anticipates the first word of the following page. It was meant to help the bookbinder or printer make sure that the leaves were bound in the right order or that the pages were set up in the press in the right order.
Source: Catchword – Wikipedia
See also: The Work of the Scribe