These are most commonly known as d evil sticks or juggling sticks and sometimes called flower sticks .
The reason they are known as devil sticks is that when you get good at tricks, it looks like the sticks are moving by magic, and therefore "the work of the devil." It's all about illusion.
Juggling Sticks are a lot of fun to make and play with, and suitable for kids (every make is a great opportunity to teach children how to use tools safely as well as developing
confidence and skills, spending quality time together and encouraging curiosity, independence and knowledge about how things work).
Cost: under $4 per set. (That's New Zealand dollars, works out at around 2.50 Euro, 2 Pounds or $3.25 US)
You can see another way of making these, with different materials here thanks to origamiwolf .
A couple of videos (not mine): simple tricks anyone can pick up in half an hour / fancy pants performance sticks (skip to 1.39 for interesting stuff; don't play with fire without proper training/supervision, and don't play on train tracks. /endpublicserviceannouncement).