Out of the infinite names of Bhagwan Shiv, he is addressed as Pinakapani, the one who yields the divine bow Pinaka with which he destroyed the invincible demons Tripurasuras. The Tripurasuras were sons of Tarakasur namely Tarakaksha, Vidyunmali and Kamalaksha. With three flying cities of Gold, Silver and Iron acquired from Brahma Ji and built by Mayasur, the architect of demons, they created havoc in the three worlds. All the gods seek protection from Bhagwan Shiv and he decides to vanquish them.
The Tripurasuras were bestowed with a boon that they could be vanquished along with their cities only when the three cities came in alignment in one line and shot with only a single arrow. As the cities were flying cities, this task was impossible to perform for anybody else but Bhagwan Shiv. But for that, he needed a great bow and an arrow.
Ordered by Brahma Ji, Viswakarma, the architect of Gods, then prepared a great bow made out of gold. Mount Meru, the king of the mountains became the bow, while Seshnaag became its string. Bhagwathi Saraswathi adorned the bow as its bell, and finally Bhagwan Vishnu became the great arrow to shoot at the Tripurasuras. At the aligned time, when all the cities of the demons came in a line for just a second and Bhagwan Shiv shot the arrow. With great speed, the arrow hit the cities in a straight line and destroyed them along with the demons. Thus, the world was saved from the atrocities of the Tripurasuras by Bhagwan Shiv and peace was restored in the three worlds.
The bow which was created by Vishwakarma was called the Pinaka, and thus Bhagwan Shiv came be to be known as Pinakapani. After destroying the demons, Bhagwan Shiv gave the divine bow to Devraj Indr, who later gifted it to the ancestors of Maharaj Janak. Thus the great bow came to be worshipped in the royal dynasty of Maharaj Janak. The bow was unsurpassable in weight and there was nobody who could lift it nor string it again.
Bhagavathi Lakshmi who was born as Mata Sita once playfully lifted the bow with ease. This surprised Maharaj Janak and also gave an enlightenment to the king regards her marriage. As he knew about the divinity of Mata Sita, he put a condition for her marriage that he would give her hand in marriage to only the warrior who could not only lift it, but also string it too.
When all the mighty warriors of the land fail, on the command of Rishi Vishwamitr, Shri Ram lifts it, thus as an incarnation of Bhagwan Vishnu becoming an yielder of it. But, respecting Bhagwan Shiv’s power, Shri Ram decides that it should not be yielded by anybody else and instead of stringing the bow, breaks it off. Thus Bhagwan Vishnu makes the Pinaka bow special and making the name of Pinakapani aptly fitting to Bhagwan Shiv.