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.