In the West, people often call a curved sword a sickle. In Greek mythology, the god Cronus used a sickle to cut off the genitals of his father's primitive god Uranus. His son Zeus was defeated by lightning and was deposed and exiled.
The sickle has always been the symbol of Kronos (Saturn in Latin). He was regarded as the god of fertility before ancient Greece. Later, people confused him with the name of Chronus, the incarnation of time.
Therefore, the image of Cronus holding a sickle (or a long-handled sickle) has become a symbol of the passage of time. In this sense, the sickle becomes a symbol of death, and it is only natural for the god of death to "choose" it as a weapon.
