Nirukta — Vedic Etymology and Word-Meaning Investigation
Nirukta ('the explained/derived meaning'; nir + ukta = 'thoroughly spoken/explained') is the fourth Vedāṅga — the science of Vedic etymology, devoted to understanding the meanings of difficult or archaic Vedic words by tracing their verbal roots and explaining their derivation.
The classical text of nirukta is Yāska's Nirukta (c. 5th century BCE), which provides etymological analyses of approximately 600 difficult Vedic words that had become obscure by Yāska's time. The Nirukta is supplemented by Nighaṇṭu — an older Vedic glossary that Yāska takes as his base text and annotates.
Yāska's fundamental principle is that Vedic words must be understood through their verbal roots (dhātus) — every Sanskrit noun and adjective ultimately derives from a verbal root, and understanding that root illuminates the theological significance of the word. For example, the name Viṣṇu is etymologized in the Nirukta tradition as 'one who pervades' (viṣ = 'to pervade') — the one who pervades all of creation. This etymology aligns precisely with the Viśiṣṭādvaita understanding of Bhagavān as the antaryāmin (inner controller) of all.
In Śrī Vaiṣṇava tradition, nirukta-style etymological meditation is deeply embedded in the āchāryas' commentaries. When Rāmānuja, Parāśara Bhaṭṭar, Nañjīyar, or Vedānta Deśika explain the meaning of a Sanskrit name or term, they routinely provide an anvarti (etymological derivation) — connecting the name to its verbal root and thereby revealing the theology the name carries. This practice is the living application of the Vedāṅga of nirukta within the living tradition.