The word yoga was derived from the Sanskrit word yuj that means ‘to join’ or ‘to unite’. This union is not just basic physical contortions of the body through bending.
For instance, when you bend over to touch your toes and your nose touches your knees that cannot be called yoga in entirety. The union is the coming together of the mind and the body. You integrate with your surroundings and nature
And ultimately, your individual thought process with the universal consciousness. We can understand more about this union once we gauge how the practise of yoga came about, how it evolved. We trace the history of yoga to the Vedic times. Its early forms can be read about in the four Vedas--- the Rig Veda, the Sam Veda, the Yajur Veda and the Atharva Veda. After that we see yogic learnings in the pre-classical period that is reflected in the Upanishads. Through various stages of Indian classicism yoga or yogic learnings have grown and evolved to reach where it is today. Lord Shiva is considered to be the first yogi. It is believed that Shiva disseminated his knowledge and learning to seven learned men called Saptarishis. They spread this knowledge in seven different directions covering diverse regions. This was knowledge that told that humans can evolve beyond their physical limitations. That is the power of yoga in a holistic way.