There may be no one knowing the source of Kabbalah. It is of the ancient times, and it got lost in time, mythology and space. It is just like other marvels that exist in the world today such as Tarot and chess. Those who are experienced Kabbalists have a belief that the basics of the spiritual system initially began on the banks of Nile River in Egypt and that happened in the past. It is said that Moses is the one who was responsible for the transformation of the wisdom and knowledge in Exodus. He did this so that he can build a society that was modern and enlightened.
Afterward, the Jewish throughout the centuries continued to practice Kabbalah. It was practiced as a branch of Judaism. The aim was to get the questions that were not addressed by Torah regulations and practices answered. At the time, there was orthodox that was deeply rooted in the society, and they would accuse the Kabbalists false thoroughly. That explains why the Kabbalist did their training in secret and later would present their teachings in the form of esoteric Bible interpretations. As you may know from history, there are spiritual and esoteric sects that have always been hunted by the mainstream religions. Such include Muslims and some Christians.
There is the traditional creation story of Kabbalah. The story relates to Adam and says that he received Kabbalah wisdom after he fell from Eden. He received the manual that explained to him how to be able to go back to heaven, and that is the Kabbalah. Afterward, Adam passed the knowledge and wisdom to his sons, and it continued to be passed from generation to generations. Finally, the understanding reached Adam, and some Kabbalists have a belief that Abraham was the one responsible for writing the first Kabbalist book which is called Safer Yetzirah or the formation book.It is believed that Moses later received the Kabbalah on Mount Sinai. It is believed he receive directly from God. There was then oral transmission from one generation to other thanks to the brilliant leaders who could not be deterred by the community who had negative thoughts about them.