The Shemhamphorasch (alternatively Shem ha-Mephorash or Schemhamphoras, originally Shem HaMephorash (שם המפורש)) is an originally Tannaitic term describing a hidden name of God in Kabbalah (including Christian and Hermetic variants), and in some more mainstream Jewish discourses. It is composed of either 4, 12, 22, 42, or 72 letters (or triads of letters), the last version being the most common.
A 12-letter variant appears in the Talmud, though it was unknown in later Kabbalah and completely absent from Jewish magic.
A 22-letter variant is first written down in Sefer Raziel HaMalakh, without interpretation, as אנקתם פסתמ פספסים דיונסים (likely transliterated as Anaktam Pastam Paspasim Dionsim). Its origins are unknown, with no connection to Hebrew or Aramaic being found, and no agreement on any particular Greek or Zoroastrian origin. There are Geonic precedents for the name, indicating that the name is older than Sefer Raziel.
A 42-letter variant was described by Hai Gaon as אדגיתץ קרעשטן נגדיכש בטרצתג חקדטנע יגלפזק שקוצית. He wrote “Although the consonants of this name are well known, its proper vocalization is not rendered by tradition. Some pronounce its first part Adgitaẓ, and others Adigtaẓ, and the last part is sometimes read Shakvaẓit, and sometimes Shekuẓit, but there is no definite proof.” This variation in pronunciation was understood by Joshua Trachtenberg to indicate that this version is quite ancient, the vowels in Hebrew being easily lost over time. It is, by some means, derived from the first 42 letters of the Hebrew Bible. Like the 22-letter name, it is found in Sefer Raziel.