Jaiminīya (Talavakāra) Brāhmaṇa 20.111

20.111

tāni sarvāṇi chandāṃsi saṃbhṛtya tairindro vṛtramahan
yanmahāntamahaṃstasmānmahānāmnayaḥ
yadaśaknottasmācchakvaryaḥ
yanmaṭviyamakarottasmānmaṭvīḥ
yatsīmānamabhinattasmātsimāḥ
atho haināssīmata eva samṛje
sima iti vai śreṣṭhamācakṣate
sima śreṣṭha svānāṃ bhavati ya evaṃ veda
tā ha vā etā indrā eva nāma
indro vai yatra mahānāmnīṣu mithunatvamaicchata | tā enamabruvansa vai naḥ
prayaccheti
kimiti
yatta etannāmeti
tābhyastatprāyacchat
tasmādetā indrā nāma
etaddha vā āsāṃ priyaṃ guhyaṃ nāma yadindrāḥ
sa yo hāsāmetadvidvānpariharata | āgāmukamenaṃ priyaṃ bhavati paśyate priyam
tasmādetā mahānāmnaya iti parokṣamākhyāyante

Having brought together all those meters, Indra slew Vṛtra with them.
Because they slew the great one (mahāntam), therefore they are the Mahānāmnīs.
Because he was able (aśaknot), therefore they are the Śakvarīs.
Because he made it intoxicating (maṭvī), therefore they are the Maṭvīs.
Because he split the boundary (sīmānam), therefore they are the Simās.
And moreover, he wiped them clean from the boundary itself.
For they call the best "sima".
He who knows thus becomes sima, the best among his own people.
These, indeed, are named "Indras".
When Indra desired pairing among the Mahānāmnīs, they said to him: "Give [it] to us!"
"What?"
"That name of yours."
He gave it to them.
Therefore these are named Indras.
For this is their dear, secret name, namely, "Indras".
He who, knowing this, avoids it—what is dear comes to him, he sees what is dear.
Therefore they are referred to cryptically as the Mahānāmnīs.