Here is a para I wrote (for an India Abroad article) on these amazing yogis from the south of India. A vast number of their books is said to have been destroyed in the several floods that swept the world...Also,these yogis also deliberately sought to be obsure, because to seek fame, when alive or dead, would have contraindicated their yogic ideals.
Here, this bit about their names, explains a lot and makes you wonder at this amazing tradition:
They even gave themselves shocking names to indicate their rebelliousness against prevailing social prejudices: one called himself Punnakkicar (The cow-dung saint) and another called himself (Kaga-pucundar, or crow's excrement), records S. N. Kandaswamy in his book The Yoga of Siddha Avvai. They encouraged an agnostic philosophy that rebelled against casteism or any systemized prejudice that sought to keep others from their birthright to mukti or liberation. They deliberately sought to shock people out of set notions, thus propelling them closer to god-realisation. The names of women Siddhas (Kudambai Cittar, Avvaiyar) indicates that this egalitarianism embraced both genders. The list that Kandaswamy presents also includes Siddhas from various religious denominations: Sufi saints (Gunangudi Mastan), Viramamunivar (actually Constantine Joseph Beshchi of Italy), Yakkobu-cittar (originally Ramdadevar) who is said to have traveled to Arabia to influence and be influenced by mystic Muslims, Teraiyar (credited with a sort of neuro-surgery) is believed to be a Buddhist, while Bhoganathar is either a Chinese or a Tamil Siddha who traveled to China to assume the name of Bo-Yang. He is also said to have traveled to Rome, Jerusalem and Rome on his mystical mission.
Tao is also a lot like Siddha Yoga -- Lao Tzu, u recall, when he felt he has done his duty by sharing his experiences, sets off on the back of a bullock, and hands over his last manuscript to a guard at the city gate. And vanishes into thin air, no one knows where he went, how he died, and where he is buried. He did not want to become famous, and was happy, being realised.
Here is a quote of his, which explains also the Siddha yogi philosophy:
A good traveler has no fixed plans, and is not intent on arriving.