The term "chopper" is used to refer to both motorcycles and helicopters, but the origin and usage of the term differ for each.
Motorcycles: The term "chopper" in the context of motorcycles originated in the 1960s and 1970s during the rise of the custom motorcycle culture. "Chopping" refers to the act of modifying or customizing a motorcycle, often by removing or "chopping" unnecessary parts, such as fenders or other non-essential components, to achieve a stripped-down and personalized appearance. Chopped motorcycles typically feature extended forks, low-slung frames, and other unique modifications. Over time, these modified bikes came to be known as "choppers."
Helicopters: In the case of helicopters, the term "chopper" comes from the distinctive sound produced by the rotor blades as they "chop" through the air. This onomatopoeic term describes the rhythmic sound made by the rotating blades and became associated with helicopters.
While both motorcycles and helicopters are referred to as "choppers," the term's origins and usage are unrelated. It's simply a coincidence that the same term is used for these two different vehicles.