"From this it follows, that the god to whom the Saxons sacrificed after their victory over the Thuringians was called Hirmin, Irmin, and in the 10th century the name was still affixed in praise or blame to very eminent or very desperate characters. Apollo is brought in by the monk, because the altar was built ad orientalem portam, and Hercules, because his pillar called up that of the native god; no other idol can have been meant, than precisely the irminsûl "(Teutonic Mythology, Jacob Grimm, Stallybrass translation)
Irmin forms part of a coumpond title of the Christian God in Heliand, Irmingott. The Old Norse version of the name Jǫrmun appears in the Poetic Edda as a byname of Woden.
Bibliogrpahy
Grimm, Jacob (Stallybrass, James translator), Teutonic Mythology, Peter Smith, Gloucester, Mass. 1976