In plain words
The Veda is the eternal scripture. 'Śāstra' means the making-known of the unknown — that is, it is directed toward revealing meanings that are beyond the senses and not [merely] established in the world, since these are not perceivable by the human intellect. 'The supreme ether, the supreme state, the Imperishable, That, Being' — so all the Śrutis, beginning with the Ṛgveda, have declared it.
In order to make known the [single, original] Veda, many Vedas came into being. The word 'Veda' at first denoted the all-knowing Supreme Lord himself, being a name for Him ('the knower, hence Veda'); afterwards, being directed toward establishing His own true nature, it also became a name ('that which reveals, hence Veda') for the body of sacred utterance resembling the all-knowing [Lord] — the Ṛgveda and the rest. Afterwards, accordingly, it came to denote what is directed toward Dharma, artha and kāma. First the term taught the Supreme Lord, who is the all-seer ('sarvadraṣṭā'); afterwards this Veda, which reveals that Supreme Lord ('darśanāt', 'from revealing'), came to denote the body of sacred utterance of the word ṛṣi as well. Afterwards, the ṛṣis, having worshipped the divine Vedas and, by that [divine] grace, having become seers, came to renown and fame.
On the strength of this, the name 'Maharṣi' too became a well-known name for the Supreme Lord. In the [thousand names attached to] the Brahmasūtra, the thousand names contain [names] such as 'Maharṣiḥ, Mukhyarṣiḥ, Śivaḥ'. Since it causes the Supreme Lord to be seen, the name 'ṛṣi' too is a fitting name for the Veda. 'Brahman' too, for the Veda,