Onam is an annual Harvest festival in the state of Kerala in India. It falls on the 22nd nakshatra Thiruvonam in the Malayalam calendar month of Chingam, which in Gregorian calendar overlaps with August–September.
Maveli was a benevolent Daitya King, and the grandson of Prahlada in Indian scriptures. The festival of Onam is celebrated in Kerala to mark his yearly homecoming after being sent down to the underworld Sutala by Vamana, a dwarf and the fifth incarnation avatar of Vishnu.
Legend of Mahabali : Mahabali was the son of Devamba and Virochana. He grew up under the tutelage of his grandfather, Prahlada, who instilled in him a strong sense of righteousness and devotion.
Maveli as Private Bus Driver in Kerala – Video Viral
https://youtu.be/Z4CsgM5E_LI
Mahabali succeeded Virochana as the king of the Asuras, and his reign over the realm was characterized by peace and prosperity. He later expanded his realm, brought the entire world under his benevolent rule.
The Devas, ruled by Lord Indra, out of jealousy, wanted to end Mahabali’s rule, they went to their patron Lord Vishnu, who agreed to take the incarnation of Vamana and go to Mahabali to end his rule.
Shukracharya, the guru and advisor of Mahabali, advised him to perform the Viswajit Yagna (Sacrifice for the Conquest of the World.)
Mahabali began the Ashwamedha Yaga at the Narmada River. The ceremony had several Brahmins present, that King Mahabali had invited. Lord Vishnu, meanwhile, adopted the avatar of Vamana, during the rite, approached Mahabali.
Mahabali, known for his generosity and as a man of his word, welcomed Vamana, and told him that he could ask for anything. Vamana, a little boy, asked for a 3 feet of land and the Asura king complied. Lord Vishnu, who had incarnated as Vamana, grew to a gigantic figure, measured Earth using one foot, and the entire universe in his next.
Mahabali, realising Vamana to be Vishnu in disguise, let Vamana place his third foot on his head causing him to drown in the netherworld, that is traditionally called Patala. Mahabali had just one wish, to be able to return to his kingdom once every year and meet his people. Vamana granted this wish and hence, during Onam, every Malayali welcomes their beloved king, preparing colourful flower carpets and sumptuous feast called Sadya.
Lord Vishnu, seeing the devotion of Mahabali, blessed him to be the Indra of the next Manvantra.
Onam is observed by all Malayalees as the return of the pious Mahabali to Kerala. Colorful aquatic festivals (e.g., boat races) are held on this occasion on the banks of the river Pampa. The celebration occurs all over Kerala and in the Malayalee diaspora. Mahabali is worshipped even in Tulunadu which consists of coastal region of Karnataka and northern Kerala. There are many pad-danas or folk songs which describe Mahabali and his deeds.
Even today, during Diwali people go to their field and call Bali Chakravarthi. It is said that Bali will come and rule this world again if some conditions are fulfilled, which are impossible in real world.