STORY OF HOW LORD SHIVA BECAME NEELAKANTHA (Story of Samudra Manthana)
During Samudra manthana (Churning of Ocean for Amrutha), lots of things emerged out of ocean. Haalaa-hala, a pot of poison was one among them. This terrified the Gods and demons as the poison was so toxic that it effects would have wiped out the entire creation. On the advice of Lord Vishnu, Gods approached Lord Shiva for help and protection as only he could swallow it without being affected. On the request of gods and out of compassion for living beings, Lord Shiva drank the poison.
However, Parvati - Lord Shiva’s consort pressed his neck so that the poison does not reach his stomach. Thus, it stayed in his throat neither going up nor going down and Shiva remained unharmed. The poison was so potent that it changed the color of Lord Mahadeva’s neck to blue. For this reason, Lord Shiva is also called Neelakantha
(the blue-necked one) where ‘Neela’ means blue and ‘Kantha’ means neck or throat. However gods also kept Lord Shiva awake during the night to avoid poison getting down into the body. Thus, Gods kept a vigil in contemplation of Lord Shiva. To amuse Shiva and to keep him awake, the gods took turn performing various dances and playing music. As the day broke out, Lord Shiva, pleased with their devotion blessed them all. Shivaratri
is the celebration of this event by which Shiva saved the world. Since then, on this day and night - devotees fast, keep vigil, sing glories of Lord and meditate.