Used metaphorically to describe reducing the intensity of actions or emotions, not just physical things. The government acted swiftly to damp down the rumors.
Pro Tip 2/3
Not silence
Doesn't mean to stop something completely, but to make it less intense. The new policy helped to damp down the public outcry without silencing the concerns.
Pro Tip 3/3
Often negative
Commonly used in contexts where something unwanted is being made less strong. The principal's announcement helped to damp down the tension among students.