The word Siddha has its origin in the Tamil word Siddhi which means 'an object to be attained' or 'perfection' or 'heavenly bliss'. India being the birth place of many traditional philosophies also gave birth to Siddha.

The system of medicine is believed to be preached by Lord Shiva to His consort Parvati, then by Her to Nandidevar who passed on the knowledge of Siddha to Siddhars for the benefit of humanity. Siddhars are people who have attained Siddhi, i.e., heavenly bliss. They developed and practised the eight levels to attain eternal bliss, viz., Astanga Yogam.

These eight levels are:

Eyamam	Good thoughts
Niyamam	Good deeds
Asanam	Posture of the body
Pranayamam	Control of breath
Prathiyakaram	Restraint of senses from their objects of enjoyment
Tharanai	Focusing of mind
Dyanam	De-concentration
Samaadhi	Super consciousness

They were also said to possess eight supernatural powers called Ashtamasiddhigal which are Anima, Mahima, Lahima, Karima, Praapti, Prahamiyam, Vasithuvam and Esathuvam. Many Siddhars are considered to have contributed to the Siddha system of medicine and among them Agathiyar is considered to be the foremost Siddhar. Their contributions were mainly classified into the following four categories:

i.	Gnanam	Spiritual knowledge
ii.	Yogam	Yogic Principles, meditation techniques
iii.	Vaatham	Alchemy and the like practices
iv.	Vaidhyam	Medical practices

Each of these practices is aimed towards maintenance of a healthy body and healthy mind which forms the basis to attain eternal bliss. The Siddha system in its unique approach stresses upon several routine and seasonal regimen as preventive measures against illness of body and mind. This system lays significant emphasis on diet as it plays a very important role in the maintenance of a healthy body - the ground which nurtures a healthy mind. The basis of this system is the physiological doctrine of three humors viz., Vaatham, Pitham and Kabham collectively known as Uyir Thathukkal. Accordingly, each individual is considered to have a unique body composition and this system of medicine has an individualistic approach in preservation of health.

Siddha traditional medicine formulations till date included in the Traditional Knowledge Digital Library are 23,016.