The crescent-shaped region of Western Asia known as the Fertile Crescent is named partly for its shape, and partly for the fertile condition of the soil in the area. The moist earth in the Fertile Crescent is in stark contrast to the earth in the arid and semi-arid surrounding areas.
The fertile crescent got its nickname from the land. The "fertile" part is there because the land had rich soil. The 'crescent" part is there because the land is shaped like a crescent, more like the crescent moon.