Pinak is the name of the bow of Shiva and this is the reason
why he is known by the name Pinaki. He used the bow to annihilate three demons that
had wreaked havoc in the world.
Story Of Pinaka - The Bow of Shiva
The three demons – Vidyumali, Tarakasha and Viryavana – had propitiated Brahma and as boon asked for immortality which was denied and later they asked for three fortified cities which could fly around and could only be destroyed with one shot of an arrow.
Shiva agreed to put an end to the rule of the flying cities. Vishwakarma built
the chariot for the mission. The Charioteer was Brahma. Earth was the body of
the chariot. Sun and Moon where the wheels of the chariots. The four Vedas
became the four steeds.
It is said that the Mount Meru became the shaft of Pinak and
Sheshnaag became the bowstring. Lord Vishnu became the arrow.
Shiva destroyed the demon cities with the Pinak bow, when it
aligned in a single line for a split of a second.