What is the origin of the idiom "damp squib" and when to use it?

The idiom "damp squib" originates from the world of fireworks, specifically a squib, which is a small explosive device used to ignite larger fireworks. A "damp squib" refers to a situation or event that turns out to be underwhelming, disappointing, or anticlimactic, much like a firework that fails to ignite due to moisture. It's used to describe something that does not live up to expectations or falls flat.