There's an article on them which unfortunately has many errors, especially in the 2nd paragraph where the author writes about dynamite, and is obviously misinformed. I have some US-made squibs somewhere but can't lay my hands on them. As I recall they are just small hand-made paper envelopes of black powder, used in rock blasting to ignite large charges of blasting powder.
The squibs mentioned in the excerpt you posted were probably home-made fireworks. They could have made a pop sound but not a sharp report like modern fireworks, since black powder does not burn instantly or detonate like modern chlorate-based pyro powder does. Some people think modern firecrackers contain black gunpowder but they do not. They contain a very dangerous mixture of chemicals like potassium perchlorate (oxidizer) and sulfur or sugar (fuel.)
I tried making all kinds of noise-making devices when I was younger, and fortunately did not have great success, or I would probably not be able to type now. I did learn that it was very difficult if not impossible to get a loud "bang" out of black gunpowder unless it was confined in a container made of very strong material, and then it was very dangerous, similar to a hand grenade.
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