Meaning of the word ‘Upanishad’
The word ‘Upanishad’ has been derived from the root Sad (to sit), to which are added two prefixes: Upa and Ni. The prefix Upa denotes nearness and Ni totality. Thus, this word means ‘sitting near by devotedly’. This no doubt refers to the pupil’s sitting down near his teacher at the time of instruction. The word in course of time gathered round it the sense of secret teaching or secret doctrine (Rahasya) which was imparted at such sittings. Upanishads are frequently spoken of as Rahasya (secret) or Guhya (mystery) also. We find in Upanishads, that due to secrecy and mystery of the teachings, a teacher refuses to impart instruction to a pupil who has not proved his worthiness to receive the instruction. Through another definition, the word primarily signifies knowledge, yet by implication it also refers to the book that contains that knowledge.