The mention of Mahavatar Babaji’s birth name as “Nagaraj” comes from M. Govindan’s book “Babaji and the 18 Siddha Kriya Yoga Tradition” published in 1991.
Ideally, I should have started with Lahiri Mahasaya . I even visited his ashram near Deogarh. But, I chose to evaluate recent material and people who are alive or their lineage alive with their Guru Shishya Parampara so that they can join to clarify and to improve the facts. I started with Marshall Govindan because somehow Iam pained that even Sadhguru is now claiming that his name in previous Janma is Nagaraja ? (Iam not able to trace this exchange). I promptly responded to Sadguru and asked him not to take the next step to declare himself to be Mahavatar Babaji.
I like Sadhguru in many many ways. But I felt he is getting in to territory which is questionable and destroying his own reputation and most importantly his good work. Sadhguru is one of extremely few Non Brahmin Teacher (Not God Man) Guru who gained Universal Popularity. He gets discouragement from established Matts including so called Dharmadhikaris. Sadguru simple logic is enough, and we don’t need to refer to more Indepth ancient “Shastras” which is called Smrithi in Dharmic Tradition. Anyone can write a Shastra and for that matter even we can question Vedas (Sruthi) as this has been tampered with and have multiple versions. I will write again on this topic separately.
Anyway, lets look at some external sources
https://www.devvratyoga.com/mahavatar-babaji/#:~:text=It%20is%20said%20that%20he,that%20he%20is%20still%20alive. (I have taken a PDF Print. Just incase if you cant access)
https://www.learnkriyayoga.com/lineage/https://yssofindia.org/about/mahavatar-babaji