This goes back a long time. The aborigines, or the original inhabitants of Australia, needed an effective weapon to hunt animals and birds for food. When they looked around, their eyes rested on wood, which was so easily available. They made banana-shaped weapons of hard wood, with a curve on top and a flat bottom. That made each leg act like an aircraft wing.
They held it from one end over their shoulders and threw it hard and straight with such force that even animals could be killed. Thus was the boomerang born.
In time, the aboriginals discovered that this little stick could be quite exciting. For instance, they discovered that if thrown in a particular manner, the boomerang curved in flight, did some neat spins in the air and returned to the thrower. They also found out that a wooden piece shaped like a T or V curves in flight. What they needed to make sure was that each leg of the boomerang was curved on top and had a flat bottom.
Throwing boomerangs, thus, became a sport with the aboriginals. That is the reason why the old hunting weapon has been transformed into a popular sport today.
The length of a boomerang varies between 12 to 30 inches and weighs about 340 grams. It has been noticed that a returning boomerang thrown by an expert thrower can travel as fast as about 100 km per hour. It creates a circle almost 45 metres wide and completes almost 10 delicate spins and loops in the air, like airplanes performing difficult stunts at an air show. And then, the boomerang returns to the thrower.
That is why the word boomerang in the English language is used to mean an action or statement that backfires.