the.com/commonplace
So ordinary it earns a yawn, yet once it meant a thought worth keeping.
means Something completely ordinary, unremarkable, or so familiar it barely registers as worth mentioning.
from From the Latin locus communis, a general argument; Renaissance scholars kept commonplace books where they copied quotable passages — so the very word for memorable lines came to mean forgettable.
Commonplace bookA personal scrapbook of quotes and ideas.
Original senseA striking passage worth saving, not dull.
Notable usersMilton, Jefferson, and Bacon kept them.