Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 45: The Churning of the Milk Ocean
Text 1.45.38
असुरास्तेन दैतेयाः सुरास्तेनादितेः सुताः।
हृष्टाः प्रमुदिताश्चासन्वारुणीग्रहणात्सुराः॥
asurās tena daiteyāḥ surās tenāditeḥ sutāḥ
hṛṣṭāḥ pramuditāś cāsan vāruṇī-grahaṇāt surāḥ
asurāḥ = are called asuras; tena = therefore; daiteyāḥ = the sons of Diti; surāḥ = suras; tena = therefore; āditeḥ sutāḥ = and Aditi’s sons; hṛṣṭāḥ = became thrilled; pramuditāḥ ca āsan = and delighted; vāruṇī-grahaṇāt = by accepting Vāruṇī; surāḥ = the demigods.
Therefore, the sons of Diti are called asuras and Aditi’s sons suras. The demigods became thrilled and delighted by accepting Vāruṇī.
This verse incidentally describes the etymology of the words sura and asura.