Once upon a time there lived a king, Mahabali. He was an Asura king who ruled the beautiful land of Kerala. Even though he was an Asura, he was a good ruler and the people looked up to him with great reverence. He was wise, judicious and extremely generous too. The people were happy and there was no discrimination on the basis of caste,color, creed or class. Rich and poor were equally treated. There was neither crime, nor corruption. There were no thieves, no poverty, sorrow or disease in the kingdom.
Seeing the growing popularity and fame of King Mahabali, the Devas became extremely jealous. They felt threatened and thought that the King would take over heaven. They approached Lord Vishnu for solace and he decided to test the King. Lord Vishnu disguised himself as a poor Brahmin called Vamana and approached the King. Mahabali always treated the brahmins with respect and asked him what he wanted. Vamana asked for a piece of land that could be covered by his three steps. Just when the King agreed, the brahmin rose to the size of cosmic proportions. The covered the earth with his first step and the skies with his second. He then asked King Mahabali for space to keep his third foot. The King bowed before Vamana and asked him to place his last step on his head so that he could keep the promise. The Brahmin placed his foot on the head and pushed him to patala lok, the underworld. Lord Vishnu revealed himself before the King Mahabali and being a true devotee of the Lord, he was mighty pleased. The Lord granted a Mahabali’s wish to see his people of Kerala once in every year. It is this day of the visit of King Mahabali to Kerala that is celebrated as Onam every year.