This is related to the time when the Lord Buddha was about to attain his enlightenment.He was attacked by Mara (a personification of evil)and his army.The Lord Buddha summoned the Goddess of the Earth to witness the attack and to save him by pointing the four fingers of the right hand to the ground. The Goddess of the Earth emerged and saved him by wringing the water of merit from her hair to drown Mara and his army. In this way Mara was Subdued.Thus this attitude is known as subduing Mara.