Who, in India, has not heard of the Banda-Chan Ramboutchi, the Houtouktou of the capital of Higher Thibet? His brotherhood of Khe-lan was famous throughout the land; and one of the most famous 'brothers' was a Peh-ling (an Englishman) who had arrived one day during the early part of this century, from the West, a thorough Buddhist, and after a month's preparation was admitted among the Khe-lans. He spoke every language, including the Thibetan, and knew every art and science, says the tradition. His sanctity and the phenomena produced by him caused him to be proclaimed a shaberon after a residence of but a few years. His memory lives to the present day among the Thibetans, but his real name is a secret with the shaberons alone.
— H.P. Blavatsky, Isis Unveiled
The Tibetan site, Tibeto-Logic, goes into extensive detail trying to answer this question and gives some interesting results. Although posted some time ago, it deserves wider notice and to be added to the list of sources discussing Blavatsky.
Read more here.