During the festival of Onam, we worship
onathappan. Could someone explain what this
onathappan signifies? If it is Mahabali, then why are there three, along with one for Thrikkakarappan?
Excerpt from this link explains in detail.
First, Thrikkakara Temple is one of the few temples in India dedicated to Lord Vamana the fifth incarnation of Lord Vishnu. It is situated in Thrikkakara, 2 kilometers east of Idapally near Cochi. The name Thrikkakkara means the holy place where Lord placed His foot. Thiru-kal-kari later became Thrikkakara
The legend is closely linked with the story of Mahabali and Lord Vishnu's Vamana or Trivikrama incarnation. Mahabali was an efficient and popular Asura king. His kingdom stretched the earth, the patala (the underground), and was threatening the skies. The gods (suras) grew worried of Mahabali's rule and popularity. Vishnu, in his avatar as Vamana, asked Mahabali for a piece of land only three paces wide. Bali, ever the generous king, granted this wish, whereupon Vamana grew to an immense size and covered the heavens with one step and the earth with another. There was no space left for Vamana to measure his third pace. "Where is my third foot of space?" asked Vamana. Tricked by this deceit, but as one who would never go back on his promises. Mahabali offered his own head for Vamana to place his third step. These events were happened at this place. As he was pushed down into Suthala, King Bali made a last request. He requested that he be allowed to visit Kerala once in a year to ensure that his people were still happy, well fed and content. Lord Vishnu was pleased to grant Mahabali his wish. Mahabali comes to visit his people and his land during Onam. This is the legend behind the Onam festival.
Hence, Onathappan is a representation of Mahabali visiting once a year, as a way of showing mutual care for the people and the land he once ruled.
Throwing of axe into the sea is just an allegory. Parasurama fought the land with Axe, from malayars(mountain people) and thirayyars(coastal people) and donated it to the brahmins who later settled as namboothris in kerala.He donated the land to brahmins in order to clean the sin of killing Kshatriyas. Before Parasurama avatar(6th avatar), it was the Vamana avatar(5th avatar). Vamana punished Mahabali Chakravarthy by sending him to Suthala. But made him the ruler of Suthala loka. Yes,Mahabali did yagna on Narmada banks. He was a not a king, but Chakravarthy who is 10 times powerful and superior than a king. His ruling area was vast, having Kerala as his Capital !