Because it makes the great bird (prāṇa) fly incessantly upward, therefore it is called Uḍḍīyāna;there the bandha is described.

This verse explains the etymology of Uḍḍīyāna.Uḍḍīnam means “fly upward.”Mahā-khagaḥ — the great bird — is a metaphor for prāṇa or Kuṇḍalinī.The Haṃsa (swan) bird traditionally represents the soul or breath.

Aviśrāntam — without rest, incessantly.When Uḍḍīyāna Bandha is applied, prāṇa continually rises towards the higher centers instead of dispersing downward or outward.

Tatra bandhaḥ — there is the bandha.The “closure” or “blocking” that makes this rise of prāṇa possible is precisely Uḍḍīyāna Bandha: the elevation of the diaphragm and the abdominal retraction that propel the energy upward.