Source : Webster's Revised Unabridged Dictionary (1913)

Commonplace \Com"mon*place`\, n.
   1. An idea or expression wanting originality or interest; a
      trite or customary remark; a platitude.

   2. A memorandum; something to be frequently consulted or
      referred to.

            Whatever, in my reading, occurs concerning this our
            fellow creature, I do never fail to set it down by
            way of commonplace.                   --Swift.

   {Commonplace book}, a book in which records are made of
      things to be remembered.

Source : WordNet®

commonplace book
     n : a notebook in which you enter memorabilia