word was
used in this sense in @Rg-Veda and in such later Vedic works as
the S'atapatha Brahmana and the B@rhadara@nyaka Upani@sad [Footnote ref 2].
The word has another derivative "yugya" in later Sanskrit literature
[Footnote ref 3].

With the growth of religious and philosophical ideas in the
@Rg-Veda, we find that the religious austerities were generally very
much valued. Tapas (asceticism) and brahmacarya (the holy vow
of celibacy and life-long study) were regarded as greatest virtues
and considered as being productive of the highest power [Footnote ref 4].

As these ideas of asceticism and self-control grew the force
of the flying passions was felt to be as uncontrollable as that of
a spirited steed, and thus the word yoga which was originally
applied to the control of steeds began to be applied to the control
of the senses [Footnote ref 5].

In Pa@nini's time the word yoga had attained its technical
meaning, and he distinguished this root "_yuj samadhau_" (_yuj_
in the sense of concentration) from "_yujir yoge_" (root _yujir_ in
the sense of connecting). _Yuj_ in the first sense is seldom used as
a verb. It is more or less an imaginary root for the etymological
derivation of the word yoga [Footnote ref 6].

___________________________________________________________________

[Footnote 1: See my _Study of Patanjali_, p. 60 ff.]

[Footnote 2: Compare R.V.I. 34. 9/VII. 67. 8/III. 27. II/X. 30. II/X. 114.
9/IV. 24. 4/I. 5. 3/I. 30. 7; S'atapatha Brahma@na 14. 7. I. II.]

[Footnote 3: It is probably an old word of the Aryan stock; compare German
Joch, A.S. geoc. l atm jugum.]

[Footnote 4: See Chandogya III. 17. 4; B@rh. I. 2. 6; B@rh. III. 8. 10;
Taitt. I. 9. I/III. 2. I/III. 3. I; Taitt, Brah, II. 2. 3. 3; R.V.x. 129;
S'atap. Brah. XI. 5. 8. 1.]

[Footnote 5: Katha III. 4, _indriya@ni hayanahu@h vi@sayate@sugocaran_.
The senses are the horses and whatever they grasp are their objects.
Maitr. 2. 6. _Karmendriya@nyasya haya@h_ the conative senses are its
horses.]

[Footnote 6: _Yugya@h_ is used from the root of _yujir yoge_ and not from
_yuja samadhau_. A consideration of Pa@nini's rule "Tadasya brahmacaryam,"
V.i. 94 shows that not only different kinds of asceticism and rigour which
passed by the name of brahmacarya were prevalent in the country at the time
(Pa@nini as Goldstucker has proved is pre-buddhistic), but associated with
these had grown up a definite system of mental discipline which passed by