The term Upanishad is derived from upa (near), ni (down) and s(h)ad (to sit), i.e., sitting down near. Groups of pupils sit near the teacher to learn from him the secret doctrine. In the quietude of the forest hermitages the Upanishad thinkers pondered on the problems of deepest concerns and communicated their knowledge to fit pupils near them. Samkara derives the word Upanishad as a substitute from the root sad, 'to loosen.,' 'to reach' or 'to destroy' with Upa and ni as prefixes and kvip as termination. If this determination is accepted, upanishad means brahma-knowledge by which ignorance is loosened or destroyed.
The treatises that deal with brahma-knowledge are called the Upanishads and so pass for the Vedanta. The different derivations together make out that the Upanishads give us both spiritual vision and philosophical argument. There is a core of certainty which is essentially incommunicable except by a way of life. It is by a strictly personal effort that one can reach the truth.
The Upanishads more clearly set forth the prime Vedic doctrines like Self-realization, yoga and meditation, karma and reincarnation, which were hidden or kept veiled under the symbols of the older mystery religion. The older Upanishads are usually affixed to a particularly Veda, through a Brahmana or Aranyaka.