Why Holika, a demoness, is worshipped on Holi? It is quite mysterious to worship Holika during Holi. Even no religious book has detailed explanation of worshipping Holika.
However in Narada Purana, Holika Dahan is mentioned which informs us about worshipping Holika and burning it with woods while singing songs.
It is written in Narada Purana "Some foolish or childish people, due to constant fear of blood sucking demons, created Holika. Hence, I worship you and seek power, wealth and prosperity for myself. Holika is a demoness and she scares Prahalad. Hence we burn her with wood and music. Burning of Holika is also symbolic of burning the year as well as sexual desires."
|Women worshiping Holika during Holi Pujan|
In the beginning Holika was protective as she was created to ward off all fears. She was symbol of power, wealth and prosperity and could bestow those to her worshippers. However she became harmful and fearsome when she tried to immolate devotee Prahalad. Hence Holika was burnt to ward off any further trouble.
Many scholars give their own explanation of word Holika and reason to worship her. Most of those interpretations zero down to burn evil even if it has power of doing good.