Which word describes a remark that is overly common and lacks freshness?

The word that describes a remark that is overly common and lacks freshness is "platitude." This term refers to a statement that has been used so frequently that it has lost its original meaning or impact, often rendering it dull or uninteresting. Platitudes are typically phrases or assertions that, while perhaps once insightful, have become trite due to their repeated use in conversation or writing. This lack of originality is what makes the term particularly fitting for the description provided in the question.

The other terms do not fit the description: "quell" means to suppress or extinguish, "quiescent" refers to a state of inactivity or dormancy, and "ruminate" means to think deeply or repeatedly about something. Each of these words has distinct meanings that do not align with the notion of a remark lacking freshness or originality.