The Shemhamphorasch is a corruption of the Hebrew term Shem HaMephorash (שם המפורש) ("the explicit Name [of God]", that is, the full and proper name, and not a filler term or cipher, which are used in conversation and prayer), which was used in tannaitic times to refer to the Tetragrammaton.
In early Kabbalah, the term was used to designate sometimes a 72-letter name for God, and sometimes a 42-letter name. Rashi said Shem ha-Mephorash was used for a 42-letter name, but Maimonides thought Shem ha-Mephorash was used only for the four letter Tetragrammaton.
A 216-letter name for God is found in Jewish Kabbalistic sources (mentioned by Tosafot as well as by the Kabbalists) as well as in Christian Kabbalah and in Hermetic Qabalah, derived from the 72 groups of three letters, each of these triplets being the name of an angel or intelligence. Spelling variants include Shemhamforash, Shemhamphorae,Shemhamphorash, Shemahamphorasch, Shemhamphoresh, Shem ha-Mephoresh, Shem ha-Mephorash,Shemhamphoresch, shem hamitfaresh.
Kabbalists and hermeticists have proposed correspondences between the 72 names of the Shemhamphorasch and a wide variety of other things, such as the Psalms, tarot cards, and so on. It is because of the flexibility (and numerical factorability) of the Shemhamphorasch that many ceremonial magicians consider it to be the key of creation of all things and all arts. The names have long been associated with 72 angels, as well as 72 demons (found in the Lemegeton or Lesser Key of Solomon), who according to the lore and legend of grimoires can create or destroy the organization or disorganization of the elements into the creation of material reality.
Read more: http://en.wikipedia.org/wiki/Shemhamphorasch