The sages at Tarugavanam(taruga forests)  were telling that the Tapas(meditation) is the best and their wives were telling that chastity is the best and were living accordingly. Lord Shiva wanted to test them. Lord Shiva went under the disguise as Bikshadanar and Tirumal went to the forest  under the disguise of a Beautiful damsel Mohini and tested the tapas of the former and the chastity of the latter. The sages got angry when they came to know with the power they got from their tapas that it was Lord Shiva as Bikshadanar tested their tapas and Tiermal as Mohini tested their wives chastity.So they got angry and made poisonous trees as sticks , immersed them in ghee and conducted a yagna with those sticks. Out of that yagna fire came lot of ferocious articles and they were directed against Lord Shiva. HE converted all of them as and when they came to Him as Dress,anklet, weapon,and garland  and kept al of them with him. When the sages came to know that all the articles directed against HIM became jewels and army for HIM they further directed further again very poisonous snakes on Lord Shiva. Those snakes in order to destroy the world with poison in their four teeth approached Lord Shiva. He first acted as if HE was frightened by them but asked them to join in his body with the other snakes which are already there in his body as jewels. Those snakes became Kanganam(auspicious thread worn around the hand), bangles in the hand,chappals and waist cord(araignan in tamil) and Lord Shiva appeared beautifully by wearing all of them. Since the snakes directed by the sages Taruga vanam  against lord Shiva frightenedhim HE is called  as BHUJANGA THRASA MOORTHI. (Bhujangam means snakes and Thrasa means to be frightened)

To worship Bhujanga thrasa moorthi we should go to the place called Perubuliyur. Lord Shiva is seen here wearing snakes as his dress. We call this form of Lord Shiva as Bhujanga Thrasa Moorthi. By worshipping him all the ill effects of Rahu planet will be nullified.  By doing BIlva archanai and offering samba food (a variety of wheat) on Thursdays one will be relieved from debt worries. By performing abhishegam with Turmeric water (Manjal neeer in Tamil) all ill effects of Raghu and sarpa kala dosham(illeffects arising out of killing snakes) will be nullified