The Sanskrit noun योग yoga is derived from the root yuj "to attach, join, harness, yoke". The word yoga is cognate with English "yoke".
The spiritual sense of the word yoga first arises in Epic Sanskrit, in the second half of the 1st millennium BCE, and is associated with the philosophical system presented in the Yoga Sutras of Patanjali, with the chief aim of "uniting" the human spirit with the Divine.
Huge Thank You to Kinni.
Text by Wikipedia.