Rudra-prasava-varṇana
The Manifestation and Naming of Rudra / Nīlalohita
पञ्चमी पञ्चम स्यैषा तनुर्नाम्नाग्निरस्तु ते / इत्युक्ते यच्छरीरस्थं तेजस्तस्योष्णसंज्ञितम्
pañcamī pañcama syaiṣā tanurnāmnāgnirastu te / ityukte yaccharīrasthaṃ tejastasyoṣṇasaṃjñitam
“O Pañcamī, let this fifth body of yours be named ‘Agni’.” When this was spoken, the radiance abiding within his body was called ‘Uṣṇa’, the sacred heat.