According to the works on Haṭhayoga and Rājayoga, kuṇḍalinī-śakti, the basic energy of a human being, lies dormant like a coiled serpent, at the base of the spinal column in the mūlādhāra-cakra. When roused by proper yogic practices, it crawls up the suṣumnā-nāḍī, the central passage for its flow, encased inside the spinal column and reaches the sahasrāra-cakra at the crown of the head. There it gets merged in Śiva, the Supreme Lord, thus giving enlightenment and bliss to the yogi.
Inside the suṣumnā-nāḍī, there are three more nāḍīs—vajriṇī, citriṇī and brahmanāḍī—concentric, one inside the other. Brahmanāḍī is the inmost of them stretching from the mūlādhāra to the pericarp of the sahasrāra.
Since the jīva (individual soul) attains Brahman (God, the Supreme) by raising his kuṇḍalinī-śakti through this nāḍī, it is called Brahmanāḍī.