Ayurveda (the science of art of healthy living) is one of the branches of Vedas. It is regarded as upaveda (offshoot) of Atharva-veda. It is a stream of the knowledge passed on from generation to generation from teachers to their students and so on. This knowledge is in a continuous flow. From where it came is not sure, who started this chain, none can tell about it. Beside teachers and students, it is passing on from a father to his son and from a mother to her daughter. It is flowing since eternity parallel to the Vedic literature that is why its emergence has been said to be from the creator (Brahma) himself. It is called eternal because nobody knows when it was not there. All this shows its long tradition and deep attachment to the Indian culture.
Etymologically Ayurveda has two word- Ayu and Veda. Ayu means life and Veda stands for the knowledge. So strictly speaking Ayurveda is knowledge for life.