The “firecracker” came from the use of a bamboo cracker. In ancient times, a beast called “Year” was believed to appear in the Eve of the New Year every year. In order to scare it away, people burned a bamboo joint in front of their house. As the air in bamboo heated, it caused the bamboo cavity to expand. The bamboo cavity eventually burst which caused large noise. People used this noise to scared away of the Beast. The term “fire cracker” (two words) came from this.
With the invention of gunpowder, gunpowder cracker replaced the bamboo firecrackers. A small amount of gunpowder was rolled into a paper roll to which a fuse, also made from gunpowder was attached. The fuse was lit and when it burned, the heat from the fire caused a chemical reaction to occur in the gunpowder that rapidly expanded the gas which burst the sides of the paper roll in a small explosion. The effects were similar to the bamboo cracker but were much more predictable.
The firecracker was safe if you held it in an open hand. However, if you close your fingers around it, you could easily lose your fingers when it exploded.
I hope that you all had a nice fourth of July and enjoyed the fireworks show near you. Please remember that in California, we are in the midst of a dry spell and everything is very dry. The danger of fire is paramount and the use of local fireworks is curtailed as a result. The safest method of enjoying the holiday is to go see a professional show rather than to “roll your own”. It only takes a few sparks to ruin your holiday festivities should your ignite a fire that was not planned; possibly on your roof. It is not fun to have your house burn down on the fourth of July just because you wanted to have a few fireworks.