Updated: Dec 9, 2022
While the race between Kartikeya and Ganesha was on, sage Agastya wanted to take two hills - Sivagiri and Sakthigiri, to his abode in the South. He gave this task to his disciple Idumban, which he gladly obliged.
Carrying the two hills like a kavadi (both hills tied to two ends of a stick), Idumban was very tired. On his way back, Idumban took a break near Palani and placed the kavadi near him.
By this time, the race was over, and Kartikeya, in anger, had left Kailasa to settle on the hill. When Idumban having taken his break, tried to lift the kavadi, he couldn't do so. Kartikeya (or Murugan) killed him in the battle that ensued, but was brought back to life.
Today, before visiting the Palani temple, pilgrims have to pay obeisance to Idumban at his shrine, halfway up the hill. If they carry a kavadi, their wishes are believed to get fulfilled.