इन्द्रियमिन्द्रलिंगमिन्द्रदृष्टमिन्द्रसृष्टमिन्द्रजुष्टमिन्द्रदत्तमिति वा

The word इन्द्रियम् (having उदात्त (acute accent) on the last) is anomalous meaning 'an organ of sense' and so called either because it is 'the characteristic from which the existence of इन्द्र is inferred' or 'it is seen by इन्द्र ' or 'it is created by इन्द्र ' or it is wished by इन्द्र ' or 'it is given by इन्द्र '.
The word इंद्रिय is a primitive word, meaning organs of sense, such as eyes &c. Its derivation is obscure, if it is a derivative word at all. In the latter alternative, it may be said to be formed by the affix घच् added after इन्द्र, in the sense of either 'a mark thereof'. As इन्द्रस्य लिङ्गम् = इन्द्रियम् ॥ The senses (indriyas) are so called because, Indra is Atma or soul, and it is inferred by the existence of the senses, eyes, ears &c. So that these organs are the 'marks or signs or linga of Indra : because they being an instrument presupose an agent, there being no instrument without an agent.

Or the senses (indriyas) are so-called because they are 'seen or known by Indra or Atma' (इन्द्रेण दृष्टं = ज्ञातं). The affix is here added to a word in the third case in construction. The knowing or perceiving of the senses by the Self is an allusion to the following Sruti of the Aitareya Upanishad Chapter 111. verse 13, where the Self having created the physical body took a survey of it. स एतमेव पुरुषं ब्रह्म ततमम पश्यदिदमदर्शमिती "He beheld this Brahma who dwells in the body who pervades everywhere, and exclaimed -- 'I have seen this'. Or they are so called because they are created by Indra or Atma (इन्द्रेण सृष्टं) i. e. the senses are formed according to the good and bad deeds of the Self. Or they are so called because they are wished for by Indra or Self (इन्द्रेण जुष्टं सेवितं) as they are the gate-ways of knowledge. Or they are so called because they are given by Indra (इन्द्रेण दत्तं) i. e. they are allotted to their respective objects by Indra e. g. the eye is given to perceive forms, the ear to perceive sounds and so on. The word वा 'or' joins every one of the above. The word इति shows, that there may be other appropriate significations also: As, इन्द्रेण दुर्जयम् = इन्द्रियम् 'senses' -- difficult to be subdued by the Soul.