1520s, "short bit of sarcastic writing, witty scoff," of unknown origin. If the meaning "small firework that burns with a hissing noise" (also 1520s) is the original one, the word might be imitative.
例文
1. The all-party meeting was a damp squib .
全党大会では期待された効果が得られなかった。
2.You know what I mean--a squib or two saying that it 's going to take place."