The boomerangs that don't return are the ones that KILL.
INTRODUCTION
The boomerang that we are commonly aware of today is a boomerang that returns back to the thrower. To those most familiar with boomerangs, it is actually called the returning boomerang. However, there is a second group of non-returning boomerangs that were used for hand to hand fighting, hunting, music and entertainment by the Aborigines. A great deal of confusion exists about boomerangs because these groups get mixed. For example, there is a commonly held impression that a boomerang can be thrown to conk an enemy on the head and then return to the thrower to be caught. This is patently false.
An understanding of the derivation of the word "boomerang" (which has been subject to revisionist history) helps to clear up this confusion.
Boomerangs are both rich in tradition and useful as modern day sport. An extended glossary of terms describe both their physical characteristics and use. For the Aborigines, boomerangs are both an item of sport and an important part of their culture.
HISTORY
The Non Returning Boomerang
The boomerang was invented between 25,000 to 50,000 years ago. The oldest boomerang, discovered in Poland, is 20,000 years old. It was the first man made object heavier than air to fly. The first boomerangs were used for hunting and killing. The hunting type could be hurled at distances of 150 to 200 yards. They hovered just above the ground at high speed killing small animals or stunning larger ones like kangaroos. These boomerangs were up to three feet across weighing 5 to 10 pounds. They were made from the roots of the mulga or wattle tree. This is because boomerangs would chip or break off if the grain of the wood didn't have the same pattern as the shape of the boomerang. The roots of these trees already had the right shape. This killing boomerang did not return.
The Returning Boomerang
The Aborigines are credited with inventing the returning boomerang. The returning boomerang probably developed over time by the Aborigines through trial and error. Prehistoric man at first would throw stones or sticks. At some point he realized that a curved stick actually created more accuracy and velocity. He then further refined and shaped these sticks to produce what became known as the hunting or fighting boomerang. At some point, certain of these boomerangs would return back to the direction of the thrower. Again, through further refinement, these lightweight boomerangs were actually caught by the first inventor of the returning boomerang. The returning boomerang, however, was always used for sport by the Aborigines.
CATEGORIES
Believe it or not, the returning boomerang is actually less accurate then the hunting and killing boomerang. All boomerangs fall into four categories:
Hunting — These are heavy. Traveling just above the ground, they can kill a small animal or stun a larger one.
Killing — These are held. They were used in hand to hand combat. Think of them as a curved club.
Music — Two are clapped together to produce a rhythm or sound effect.
Returning — Originally made of wood, most of these boomerangs are now made of plastic or resin using computer technology.
http://www.culturequest.us/aboriginal_tools/boomerang.htm