Commonly the term aṇḍa (anda) means ‘egg’ or ‘a bird’s egg’ to be specific. In a famous verse in Ṛgveda (Rigveda) we find a figure of speech based on comparison: “As a bird brings out its progeny breaking the egg…” — āṇḍeva bhitvā śakunasya garbham. This comparison considers the egg  or aṇḍa as another womb of the bird.

In a similar way, Mahābhārata (Mahabharata), while describing the Creation, imagines a Great Egg or aṇḍa even before the very onset of the procedure of the creation of the universe. At the beginning of the epic we find Ugraśravā (Ugrasrava) Sauti describing the genesis of the universe. He said that before the universe came to exist, there was a vast void shrouded in darkness which light could not penetrate. In this darkness manifested a Great Egg, the aṇḍa, which was the seed of the Creation and encapsulated the germ of all the elements of the world. This aṇḍa, eternal and imperishable, encapsulating the germ of the universe, was the first manifestation out of the abstract void – it was the first evolute —

niṣprabhe’smin nirāloke sarvatastamasāvṛte
bṛhadaṇḍamabhūd ekaṃ prajānāṃ vījamavyayam.

This Great Egg, also called bṛhadaṇḍa (brihadanda), is known as hiraṇyagarbha (hiranyagarbha; ‘the Golden Germ’) in philosophy. Manusaṃhitā (Manusamhita) calls it hemamaya aṇḍa (‘the Golden Egg’) — tadaṇḍamabhavad haimam.

Although the names differ in the texts, the process of the Creation itself has been described to be identical in all the texts. Manusaṃhitā also recounts that before the Creation there existed a dark void with the essence of the abstract and providing no imaginable or identifiable concrete form of manifestation. The one element identifiable amidst this darkness was water. That is why the state after mahāpralaya (mahapralaya; ‘the end of the world after the doomsday’) has been imagined to be nothing but the cosmos immersed in water. According to Manu, the divinely charged semen of the Supreme Being was thrown into this water and it led to the materialisation of the Golden Egg which had a glow of a thousand Sun —

āsīdidaṃ tamobhūtam aprajñātamalakṣaṇam
apratarkamavijñeyaṃ prasuptamiva sarvataḥ.
apa eva sasarjādau tāsu vījamavāsṛjat
tadaṇḍamabhavadhaimaṃ sahasrāṃśusamaprabhaṃ.
tasmin yajñe svayaṃ brahmā sarvaloka pitāmahaḥ.

In fact, the Puranic concept of the vast darkness of the pre-Creation stage stems from the ideas found in Ṛgveda — tama āsīttamasā gūḍhamagre.

And Ṛgveda also records the manifestation of the Golden Germ or hiraṇyagarbha out of that darkness — hiraṇyagarbhaḥ samavartatāgre.

The first evolute of the Creation was hiraṇyagarbha. Hiraṇyagarbha is the term by which the Great Egg or bṛhadaṇḍa (in Mahābhārata) is commonly referred to. 

Arguably the analogy of the Creation being born out of the water after the divine semen is discharged into the water is derived from the biological image of the male seed inseminating the ovum in the womb, the embryo growing in the womb and ultimately being born. The image of the water as the womb nurturing the embryonic Creation is the first phase in the process of Creation of brahmāṇḍa (brahmanda). Various verses in Ṛgveda also mention this phase. 

In the second phase comes the state of hiraṇyagarbha. The organ (and the state of the embryo therein) of the womb is also known as ulva in Vedic Sanskrit and in the terminology of āyurveda (ayurveda); and that very thing is customarily called garbha or aṇḍa. One can also argue that because the phenomenon under discussion here, i.e. the Great Egg, is not an egg or embryo per se, the glorifying adjective of hiraṇya (hiranya; ‘golden’) has been appended with the root garbha.

One of the most ancient and authentic texts, Śatapatha Brāhmaṇa (Satapatha Brahmana), while giving the account of mahattatva or mahān (mahan; ‘God’s existence and Creation’), mentions three stages of mahattatva and that there existed water before everything else — āpo ha vā idamagre salilemevāsīt. Then emerged the Golden Egg in that vast water body — hiraṇmayamaṇḍaṃ samvabhūva. Thereafter manifested a deity who was hailed as Prajāpati (Prajapati) — puruṣaḥ samabhavat sa prajāpatiḥ

In connection with the manifestation of the perceptible existence of the universe from the abstract cosmos, the Purāṇa (Purana) texts also corroborate the view of the VedasBrāhmaṇas and Mahābhārata that bṛhadaṇḍa was the first evolute in the process of the separation of the concrete universe with an individual identity from the non-representational Being. The Purāṇa authors, drawing a parallel with the womb, imagined hiraṇyagarbha to be a wonderful and incomparable Golden Egg emerging out of the abstract Nature. This Egg is encapsulated by water. That water is encased in tejas (fire or heat), the tejas in the air, the air in the firmament, the firmament in pañcabhūta (panchabhuta; ‘the five elements of Nature’). And pañcabhūta is guarded by Nature, the abstract, around the Divine Existence. In fact, these consecutive protective layers of the Golden Egg manifest in this particular order out of the Golden Egg itself, because bṛhadaṇḍa itself is a manifestation of mahattatva or mahān, the Divine existence. Bṛhadaṇḍa in various stages is called buddhi, hiraṇyagarbha, mahān, biriñci and so on. And last, but not least, to say is that this very aṇḍa is brahmāṇḍa (brahmanda; ‘the universe’).