Onam - Most popular festival in Kerala Onam is is the National festival of Kerala. Onam is the most popular festival in 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 word Onam is believed to have been originated from the Sanskrit word Shravanam which in Sanskrit refers to one of the 27 Nakshatars 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 festival of Onam is dedicated to the King Mahabali who though was an Asur (one with more negative thoughts in his mind) by birth but was a Sur (one with more positive thoughts in his mind) by virtue. It is said t