How Upanishad became the recognised name of the philosophical treatises contained in the Veda is difficult to explain. Most European scholars are agreed in deriving upa-ni-shad from the root sad, to sit down, preceded by the two prepositions ni, down, and upa, near, so that it would express the idea of session, or assembly of pupils sitting down near their teacher to listen to his instruction. In the Trikândasesha, upanishad is explained by samipasadana, sitting down near a person.
Such a word, however, would have been applicable, it would seem, to any other portion of the Veda as well as to the chapters called Upanishad, and it has never been explained how its meaning came thus to be restricted. It is still more strange that upanishad, in the sense of session or assembly, has never, so far as I am aware, been met with. Whenever the word occurs, it has the meaning of doctrine, secret doctrine, or is simply used as the title of the philosophic treatises which constitute the gñânakânda, the knowledge portion, as opposed to the karmakânda, the work or ceremonial portion, of the Veda.
Native philosophers seem never to have thought of deriving upanishad from sad, to sit down. They derive it either from the root sad, in the sense of destruction, supposing these ancient treatises to have received their name because they were intended to destroy passion and ignorance by means of divine revelation, or from the root sad, in the sense of approaching, because a knowledge of Brahman comes near to us by means of the Upanishads, or because we approach Brahman by their help. Another explanation proposed by Sankara in his commentary on the Taittirîya-upanishad II, 9, is that the highest bliss is contained in the Upanishad (param sreyo 'syâm nishannam).
These explanations seem so wilfully perverse that it is difficult to understand the unanimity of native scholars. We ought to take into account, however, that very general tendency among half-educated people, to acquiesce in any etymology which accounts for the most prevalent meaning of a word. The Âranyakas abound in such etymologies, which probably were never intended as real etymologies, in our sense of the word, but simply as plays on words, helping to account somehow for their meaning. The Upanishads, no doubt, were meant to destroy ignorance and passion, and nothing seemed more natural therefore than that their etymological meaning should be that of destroyers.
The history and the genius of the Sanskrit language leave little doubt that upanishad meant originally session, particularly a session consisting of pupils, assembled at a respectful distance round their teacher.
With upa alone, sad occurs as early as the hymns of the Rig-veda, in the sense of approaching respectfully:—
Rig-veda IX, 11, 6. Nâmasâ ít úpa sîdata, “approach him with praise.” See also Rig-veda X, 73, II; I, 65, I.
In the Khândogya-upanishad VI, 13, I, a teacher says to his pupil, atha mâ prâtar upasîdathâh, “come to me (for advice) tomorrow morning.”
In the same Upanishad VII, 8, I, a distinction is made between those who serve their teachers (parikaritâ), and those who are admitted to their more intimate society (upasattâ, comm. samîpagah, antarangah, priyah).
Again, in the Khândogya-upanishad VII, I, we read of a pupil approaching his teacher (upâsasâda or upasasâda), and of the teacher telling him to approach with what he knows, i.e. to tell him first what he has learnt already (yad vettha tena mopasîda).
In the Sûtras (Gobhilîya Grihya-sûtra II, 10, 38) upasad is the recognised term for the position assumed by a pupil with his hands folded and his eyes looking up to the teacher who is to instruct him.
It should be stated, however, that no passage has yet been met with in which upa-ni-sad is used in the sense of pupils approaching and listening to their teacher. In the only passage in which upanishasâda occurs (Ait. Âr. II, 2, 1), it is used of Indra sitting down by the side of Visvâmitra, and it is curious to observe that both MSS. and commentaries give here upanishasasâda, an entirely irregular form.
The same is the case with two other roots which are used almost synonymously with sad, viz. âs and vis. We find upa+âs used to express the position which the pupil occupies when listening to his teacher, e.g. Pân. III, 4, 72, upâsito gurum bhavân, “thou hast approached the Guru,” or upâsito gurur bhavatâ, “the Guru has been approached by thee.” We find pari+upa+âs used with regard to relations assembled round the bed of a dying friend, Khând. Up. VI, 15; or of hungry children sitting round their mother, and likened to people performing the Agnihotra sacrifice (Khând. Up. V, 24, 5). But I have never met with upa-ni-as in that sense.
We likewise find upa-vis used in the sense of sitting down to a discussion (Khând. Up. I, 8, 2), but I have never found upa+ni+vis as applied to a pupil listening to his teacher.
The two prepositions upa and ni occur, however, with pat, to fly, in the sense of flying down and settling near a person, Khând. Up. IV, 7, 2; IV, 8, 2. And the same prepositions joined to the verb sri, impart to it the meaning of sitting down beneath a person, so as to show him respect: Brih. Âr. I, 4, II. “Although a king is exalted, he sits down at the end of the sacrifice below the Brahman,” brahmaivântata upanisrayati.
Sad, with upa and ni, occurs in upanishâdin only, and has there the meaning of subject, e.g. Satap. Brâhm. IX, 4, 3, 3, kshatrâya tad visam adhastâd upanishâdinîm karoti, “he thus makes the Vis (citizen) below, subject to the Kshatriya.”
Sometimes nishad is used by the side of upanishad, and so far as we can judge, without any difference of meaning.
All we can say therefore, for the present, is that upanishad, besides being the recognised title of certain philosophical treatises, occurs also in the sense of doctrine and of secret doctrine, and that it seems to have assumed this meaning from having been used originally in the sense of session or assembly in which one or more pupils receive instruction from a teacher.
Thus we find the word upanishad used in the Upanishads themselves in the following meanings:
1. Secret or esoteric explanation, whether true or false.
2. Knowledge derived from such explanation.
3. Special rules or observances incumbent on those who have received such knowledge.
4. Title of the books containing such knowledge.
I. Ait. Âr. III, 1, 6, 3. “For this Upanishad, i.e. in order to obtain the information about the true meaning of Samhitâ, Târukshya served as a cowherd for a whole year.”
Taitt. Up. 1, 3. “We shall now explain the Upanishad of the Samhitâ.”
Ait. Âr. III, 2, 5, 1. “Next follows this Upanishad of the whole speech. True, all these are Upanishads of the whole speech, but this they declare especially.”
Talav. Up. IV, 7. “As you have asked me to tell you the Upanishad, the Upanishad has now been told you. We have told you the Brâhmî Upanishad,” i.e. the true meaning of Brahman.
In the Khând. Up. III, II, 3, after the meaning of Brahman has been explained, the text says: “To him who thus knows this Brahma upanishad (the secret doctrine of Brahman) the sun does not rise and does not set.” In the next paragraph brahma itself is used, meaning either Brahman as the object taught in the Upanishad, or, by a slight change of meaning, the Upanishad itself.
Khând. Up. I, 13, 4. “Speech yields its milk to him who knows this Upanishad (secret doctrine) of the Sâmans in this wise.”
Khând. Up. VIII, 8, 4. When Indra and Virokana had both misunderstood the teaching of Pragâpati, he says: “They both go away without having perceived and without having known the Self, and whoever of these two, whether Devas or Asuras, will follow this doctrine (upanishad), will perish.”
II. In the Khând. Up. I, i, after the deeper meaning of the Udgîtha or Om has been described, the advantage of knowing that deeper meaning is put forward, and it is said that the sacrifice which a man performs with knowledge, with faith, and with the Upanishad, i.e. with an understanding of its deeper meaning, is more powerful.
III. In the Taittirîya-upanishad, at the end of the second chapter, called the Brahmânandavallî, and again at the end of the tenth chapter, the text itself says: “Ity upanishad, this is the Upanishad, the true doctrine.”
IV. In the Kaushîtaki-upanishad II, I; 2, we read: “Let him not beg, this is the Upanishad for him who knows this.” Here upanishad stands for vrata or rahasya-vrata, rule.
 Pânini I, 4, 79, has upanishatkritya.
 M. M., History of Ancient Sanskrit Literature, p. 318; Colebrooke, Essays, I, 92; Regnaud, Matériaux, p. 7.]
 The distinction between possible and real etymologies is as modern as that between legend and history.
 See M. M.'s History of Ancient Sanskrit Literature, p. 318.
 See also Khand. Up. VI, 7, 2.
 Mahâbhârata, Sântiparva, 1613.