It literally means “the womb of the universe,” “the womb of everything that is,” or the prime abode, the source. It is the Sanskrit name for God, the essence, that from which everything comes. It is the name of the Hindu god, Krishna.
The Bhagavad Gita was written around the 3rd century BC, about 2300 years ago. There are few references to the word “yoga” before the Gita. There are a lot more afterwards. Before, the texts that use the word “yoga” simply use it in the context of yoking or uniting, putting two things together. In the Vedas, it is used that way. There are a few references to yoga before the Gita, but they’re vague. You could say the word “yoga” comes into vogue as a spiritual practice with the Bhagavad Gita.
The Bhagavad Gita is this tiny little section in the middle of the Mahabharata where Arjuna, the main character, feels threatened during battle. A lot of people think that Arjuna got scared, but Arjuna could fight battles single-handedly against an entire army. What he saw that scared him wasn’t the sight of some big army: it was the transformation that the battle would bring. It was who he would be when the battle was over, what he would lose in the fight. The battle lasted 18 days; there are 18 chapters in the Bhagavad Gita. In each chapter, Arjuna asks questions.
Swami Kripalu said that every yogi and yogini who travels this path will have to ask these very same questions to a teacher. They are the questions that come up borne out of practice. If you are sincerely practicing, and you go deep enough, you will have to ask questions, like Arjuna. Most of the questions are hidden; there is a hidden meaning in those questions. If you look at them in a deeper way, they are questions about the path. Krishna, in the Bhagavad Gita, , lays out the yogic path for Arjuna on the battlefield and an understanding of how to go down into the darkness inside, fight the demons, and free the earth, which is your self.