According to HPB, the texts of Kiute are among the instructions given to those who belong to the Trans-Himalayan school she was connected with. It is the source of the Stanzas of Dzyan that form the basis of her Secret Doctrine. The earliest use of the term Kiute, which is a phonetic representation of the Tibetan rGyud-sde (Tantra), appears to be in Capuchin missionary Orazio della Penna’s 1730 “Brief Account of the Kingdom of Tibet.” It was translated into English as an Appendix to Clements R. Markham’s Narratives of the Mission of George Bogle to Tibet, and of the Journey of Thomas Manning to Lhasa, published by Trubner and Co., London, 1876. It appears on page 334 where the 38 volumes of Khiute are mentioned, and then on page 338 where the following is found:
The other part of the thirty-six volumes of the law of Khiute gives precepts for practicing magic, and other foul matters of luxury and lust; and the monks and followers of this Khiute have monasteries and a temple, and rooms for the Lama or superior of the convent, but the monks eat and drink in common in the said temple. I have not read this infamous and filthy law of Khiute, so as not to stain my mind, and because it is unnecessary. For to confute it one must know in the abstract of what it treats, and there is little good or indifferent that is not mixed up with much more witchcraft, magic incantations, and obscenity.…This law of Khiute is the shortest road to holiness, but it is uncertain and rough, because those who observe well the precepts of this law, and practice that which it teaches, can became saint in one life without any other transmigrations.
Not much of a source to plagiarize from, as her critics charge. The entry in the Norwegian Wikipedia takes up the matter of the source of the book of Dzyan. A translation of the surprising results is here.