‘Lock’ is a poor translation of bandha, yet unfortunately it is still used in most yoga circles today. The word bandha suggests the act of capturing, tethering, tying, or harnessing. It implies a catch that must ultimately include release. The act of bandha involves its correlate, abandha, which means to unfasten or liberate. Physilogically the aim of the bandhas is to open and release the breathing mechanism and to promote proper metabolic flow through the adjoining organs, glands and vessels.
Tias Little – Yoga of the Subtle Body