Holika (Sanskrit: होलिका) was a demoness in Hindu mythology who was burnt to death with help of God Brahma by Prahlad. She was the sister of King Hiranyakashipu.
Myth
According to Hindu mythology, there was a king named Hiranyakashipu whose desire was to be seen as a great man. To fulfill his desire he did the required Tapas (penance) and was granted a boon by Brahma.
Once invincible, Hiranyakashyapu ordered people in his kingdom to worship him as a God. Everyone obeyed with the exception of his son Prahlad. Prahlad refused to see his father as a god and stayed devoted to Vishnu.
This made Hiranyakashipu very angry and he made various attempts to kill Prahlad. During a particular attempt on Prahlad's life, King Hiranyakashyapu called upon his sister Holika for help. Holika had a special gift that prevented her from being harmed by fire. Hiranyakashyapu asked her to sit on a bonfire with Prahlad on her lap in the hope that this would kill Prahlad. Holika was not aware that the boon worked only when she entered the fire alone. Prahlad, who kept chanting the name of Lord Naarayana all this while, came out unharmed, as the lord blessed him for his extreme devotion. Thus, Holi derives its name from Holika. And, is celebrated as a festival of victory of good over evil.
Holi is also celebrated as the triumph of a devotee. As the legend depicts that anybody, howsoever strong, cannot harm a true devotee. And, those who dare torture a true devotee of god shall be reduced to ashes.