|The following is based on Fallout Tactics and is not canon.|
A boomerang is a thrown tool for hunting, a flat airfoil made of wood, it is designed to spin about on its axis perpendicular to the direction of flight. Assuming this is a returning boomerang, if it misses its target it will circle back to the thrower, making it reusable. With enough force behind it, 2 lbs. of wood can prove an effective weapon, and the requirements to wield it effectively are relatively low.
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Behind the scenes
Though boomerangs are commonly thought of as an Australian icon, many cultures throughout history have used throwing sticks and boomerang-like weapons, including Native Americans. Although not a common sight in pre-War America, it is still unusual that they are still found.