Yoga1 is translated from the Sanskrit as "yoke". The yoke to which the word refers is the connection between the Atman, the conscious or personal experience of the divine nature, and Brahman, the superconscious or transpersonal experience of divinity, or the Godhead. 
There are innumerable "yogas" found and practiced within the various spiritual traditions of the world, both East and West. "Yoga" has come to be typically and specifically discussed in reference to the spiritual traditions and practices associated with India, namely Hinduism, Jainism, Buddhism, and Vedanta. 
A soapstone seal soapstone seal from the Indus Valley archeological site of Mohenjo-Daro depicting a horned or headressed figure surrounded by four animals, and seated on a throne in what may be interpreted as a yogic or meditative posture, specifically badha konasana or "bound angle". The figure is often identified with Shiva, perhaps in his role as Pashupati ("Lord of Animals"), and this interpretation suggests that Yoga was known in the Indian subcontinent from 2600 to 1900 B.C.
Yoga in modern times
In 1893, Swami Vivekananda, disciple of Ramakrishna, spoke before the World Parliament of Religions, mentioning the need for a more universalistic approach to spirituality. While Vivekananda's allegiance lay primarily with Vedanta, his remarks sparked considerable interest.
In 1920, Paramahansa Yogananda also went to the United States, held many conferences and made a lot to popularize Yoga and Kriya Yoga, especially through his famous book "Autobiography of a Yogi", first published in 1946 and still a bestseller. This book gives a good overview of what Yoga is about.
By the twentieth century, Yogis became objects of both reverence and scientific research in the West as they availed themselves to the Sixties counter-culture movement and demonstrated themselves able to regulate involuntary activities such as heart-rate, blood pressure, and body temperature. The first of these individuals to be studied in the West was Swami Rama, at the Menninger Institute.
- Feuerstein, G. (1996). Shambhala Guide to Yoga Boston:Shambhala Publications.
- Feuerstein, G.; Wilber, K. (2001). The Yoga Tradition: Its History, Literature, Philosophy and Practice. Hohm Press.
1 Yoga (योग), derived from the Sanskrit yugam, a cognate of the modern English "yoke" (iugum, Latin). Its Proto-Indo-European forebearer is speculated to be *yugom, from the root *yeug- (yuj-, Sanskrit) meaning "to join" or "unite".