The constellation Leo gets its name from the Nemean Lion of Greek mythology. The Greek astronomer Ptolemy was the first in the west to catalogue this constellation. Evidence suggests that others, notably Mesopotamians and Babylonians, may previously have recognized a constellation called "The Lion."
According to Greek mythology, the Nemean Lion killed and terrorized the inhabitants of Nemea. It lived in a cave and had protective skin that could not be pierced by weapons. To relieve the Nemeans from oppression, Hercules trapped the Lion in its cave and strangled it with his bare hands. This was the first of his 12 labors.