Manusmriti
आपो नारा इति प्रोक्ता आपो वै नरसूनवः । ता यदस्यायनं पूर्वं तेन नारायणः स्मृतः ॥ १० ॥
The waters are called narah, (for) the waters are, indeed, the offspring of Nara; as they were his first residence (ayana), he thence is named Narayana.
english translation
Apo nArA iti proktA Apo vai narasUnavaH । tA yadasyAyanaM pUrvaM tena nArAyaNaH smRtaH ॥ 10 ॥
hk transliteration by Sanscript