Kannappa Nayanar

Thinnan was born into the Vettuvar [Hunter] community in Uduppur close to Tirupati. He was a staunch devotee of God Kalathinathan of Kalahasthi Hill. He would diligently worship the Lingam with a pure heart, unaware of the correct rituals. He would store water in his mouth and pour it on the Lingam as Abhishekam. He would collect flowers on his matted head and offer them to the Lord after removing the old flowers with his feet. Finally, he would offer meat as Naivedhyam to his Lord.

Lord Shiva wanted to put Thinnan’s intense devotion to test, so that its true glory may be understood by all. One day, blood started oozing out from one of the eyes of the Lingam. Alarmed, Thinnan got some herbs and kept on the eye but the bleeding did not stop. Thinnan scooped out his own eye and kept it on the bleeding eye of the Lingam. The bleeding stopped. Soon, the other eye of the Lingam started bleeding. Thinnan, without hesitation was about to pluck out his other eye when suddenly Lord Siva caught hold of his hand and said: ‘My dear child, Kannappa! Stop plucking your eye.’ Tinnanan thus became Kannappa, because he gave his own eye to the Lord. Kannappa also regained his vision.

References:
shaivam.org
http://www.dlshq.org/download/nayanar.htm