The word Yoga comes from root Vedic Sanskrit word Yuj, which means The Path. However, the Yoga, as we know it today, i.e., as an exercise, is Ashtanga Yoga. Also, Patanjali did not invent the Ashtanga Yoga as it is wrongly believed by many. Patanjali’s Yoga Sutras are mostly a collection of teachings from various Rishis and Rishikas who preferred to stay aloof from the material world by shunning all sorts of recognition. Even the four Vedas were written by such sage men and women, who sought the solitude of the woods rather than adoration and appreciation of the masses. Krishna Dwaipayana Vyasa a.k.a. Vyasa a.k.a. Veda Vyasa only compiled and probably edited the texts for mass consumption.
Vedic knowledge and wisdom are in no ways a ‘Holy Book’ sent by God(s) or Goddess(ess) via some prophet or messiah. There is no concept of heaven in the skies nor a hell below the earth in the Vedic texts.
Swarga often confused as Heaven, and Naraka, misunderstood as Hell, is all within us. Everything is inside our minds, which, through thoughts, inspires actions before manifesting experiences. So, if your Mana, or Mind, is full of ideas driven by knowledge and wisdom it is sure to result in a life of Swarga, and if your Mind is replete with ignorance and stupidity, you are sure to experience Naraka right in this life.