Onam is the most popular festival in Kerala celebrated by all Malayalis all around the world equally without distinction of religion or caste; with great pomp and show. It is believed to be the National festival of Kerala. Onam is celebrated each year in the month of August-September which according to the Malayalam calendar is the first month of the year called Chingam. The festivities of the Onam last for ten days in which old and young participate with equal enthusiasm. The festival is celebrated to commemorate King Mahabali, whose spirit is said to visit Kerala at the time of Onam.
The word Onam is believed to have been originated from the Sanskrit word Shravanam which in Sanskrit refers to one of the 27 Nakshatras or constellations. Thiru in South India is used for anything associated with the Lord Vishnu and Thiruvonam is believed to be the Nakshatra of Lord Vishnu who pressed the great King Mahabali to the underworld with his foot.
The legend of Onam is that during the reign of the mighty asura (demon) king, Mahabali, Kerala witnessed its golden era. Everybody in the state was happy and prosperous and the king was highly regarded by his subjects. Apart from all his virtues, Mahabali was egoistic. This weakness in his character was utilized by Gods to bring an end to his reign as they felt challenged by Mahabali’s growing popularity. However, for all the good deed done by Mahabali, God granted him a boon that he could annually visit his people with whom he was so attached. According to Vaishnavism mythology, the defeated Devas approached Vishnu for help in their battle with Mahabali.
Vishnu refused to join the gods in violence against Mahabali because Mahabali was a good ruler and his own devotee. He, instead, decided to test Mahabali’s devotion at an opportune moment. Mahabali, after his victory over the gods, declared that he will perform Yajna (homa sacrifices) and grant anyone any request during the Yajna. Vishnu took the avatar of a dwarf boy called Vamana and approached Mahabali. The king offered anything to the boy & gold, cows, elephants, villages, food, whatever he wished. The boy said that one must not seek more than one needs, and all he needs is the property right over a piece of land that measures & three paces. Mahabali agreed.
The Vamana grew and covered everything Mahabali ruled over in just two paces. For the third pace, Mahabali offered himself, an act which Vishnu accepted as evidence of Mahabali’s devotion. Vishnu granted him a boon, by which Mahabali could visit again, once every year, the lands and people he previously ruled. This revisit marks the festival of Onam, as a reminder of the virtuous rule and his humility in keeping his promise before Vishnu.