Koot Hoomi (also spelled Kuthumi, and frequently referred to simply as K.H.) is one of the Mahatmas that inspired the founding of the Theosophical Society. He engaged in a correspondence with two English Theosophists living in India, A. P. Sinnett and A. O. Hume, correspondence was published in the book The Mahatma Letters to A. P. Sinnett.
Little descriptive references to K.H. occur in The Mahatma Letters to A. P. Sinnett and the writings of Mme. Blavatsky. The name Koot Hoomi seems to be a pseudonym. We find a reference to a "Rishi Kuthumi" in several Puranas, as for example in the Vishnu Purana (Book 3, Chapter 6) where he is said to be a pupil of Paushyinji. In reference to this Mme. Blavatsky wrote:
The name of Rishi Koothumi is mentioned in more than one Purana, and his Code is among the 18 Codes written by the various Rishis and preserved at Calcutta in the library of the Asiatic Society. But we have not been told whether there is any connection between our Mahatma of that name, and the Rishi, and we do not feel justified in speculating upon the subject. All we know is, that both are Northern Brahmans, while the Môryas are Kshatriyas.
K.H.'s early letters to Sinnett are signed with the name Koot Hoomi Lal Sing. However, later in the correspondence, he says the "Lal Singh" was an addition made by his disciple Djwal Khool:
Why have you printed The Occult World before sending it to me for revision? I would have never allowed the passage to pass; nor the "Lal Sing" either foolishly invented as half a nom de plume by Djwal K. and carelessly allowed by me to take root without thinking of the consequences. . .
In an interview by Charles Johnston to H. P. Blavatsky, he described the handwriting of Master K.H. in the following way: