Prāṇāyāma (Sanskrit: प्राणायाम, prāṇāyāma) is a Sanskrit word meaning “extension of the prāṇa or breath” or, “extension of the life force”. The word is composed of two Sanskrit words, Prana, life force, or vital energy, particularly, the breath, and “ayāma”, to extend or draw out. (Not ‘restrain, or control’ as is often translated from ‘yam’ instead of ‘ayāma’). The origin of this yogic discipline lies in ancient Bharat (India) and what is known as present day Hinduism.
From Yoga Journal:
Pranayama, the formal practice of controlling the breath, lies at the heart of yoga. It has a mysterious power to soothe and revitalize a tired body, a flagging spirit, or a wild mind. The ancient sages taught that prana, the vital force circulating through us, can be cultivated and channeled through a panoply of breathing exercises. In the process, the mind is calmed, rejuvenated, and uplifted. Pranayama serves as an important bridge between the outward, active practices of yoga—like asana—and the internal, surrendering practices that lead us into deeper states of meditation.