The Collaborative International Dictionary of English v.0.48:

Offcut \Off"cut`\, n.
   1. That which is cut off.
      [1913 Webster]

   2. (Bookbinding) A portion of the printed sheet, in certain
      sizes of books, that is cut off before folding.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Inset \In"set\, n.
   1. That which is inserted or set in; an insertion.
      [1913 Webster]

   2. (Bookbinding) One or more separate leaves inserted in a
      volume before binding; as:
      (a) A portion of the printed sheet in certain sizes of
          books which is cut off before folding, and set into
          the middle of the folded sheet to complete the
          succession of paging; -- also called offcut.
      (b) A page or pages of advertisements inserted.
          [1913 Webster]