There is a wide-spread theory that has been around … for a long time now — at least since I first started to seriously research native Germanic belief back in the early 90’s — that links Tacitus’ Irmin to the better known Germanic god Tiw (Old Norse – TyR). As I was strongly drawn to Tiw in my early years, I was initially as hungry as a wolf for whatever lore I could muster on him; Irmin, Seaxneat, the Suebian “God and Ruler of All” … you name it, I was an eager-beaver when it came to anything that could be even remotely connected to him. No matter if it be by actual evidence or mere authoritative suggestion. Of course, as the information continued to flow in I constantly went back to reevaluate various pet notions that ultimately gave sincerity the upper hand over zeal, and led to a reevaluation of my opinion on the matter.
In the end I had to conclude that it was, at best, unlikely that Irmin was one of Tiw’s by-names. Why, you ask?
Well, for one, the Norse-Icelandic Eddas make a concrete connection between Irmin and the god Woden; ranking the former’s Old Norse cognate, ie. Jormun, among the latter’s many, many by-names.
Disputing this, people will often cite the theoretical ascension of the cult of Woden and it’s absorption of various elements of the cult of Tiw. And while I do happen to agree with the gist of this theory, I really don’t like to reach when a more viable answer is right at hand. I certainly don’t mind well-founded theories, but when one starts formulating theories based on theories, and offering it up as ancestral belief, I begin to get a little shy.
Getting back to the actual evidence left to us by the ancestors, we have the 10th century writings of the Old Saxon monk Widukind of Corvey, who references the Saxon Irminsul and states that it was erected in honour of Hermes, whom the Saxons call Hermin, ie. Irmin, but whom they worship as Mars. Now, it was Woden who was equated with the Roman Mercury, who was in turn equated with the Greek Hermes. Mars on the otherhand was the customary gloss for Tiw, but we do know that as early as the 1st century AD the Germanic Mercury, ie. Woden, was being worshiped alongside the Germanic Mars, ie. Tiw, in the “cult of war”, and so must even then have had a clear martial association. Indeed, from the Migration Age forward we can plainly see that it is Woden who dominates the lore of warfare, the “port of Mars”; with Tiw’s continued association with war being limited to a mere mythic reference or two, but never actually seen or heard of in history, legend or the archaeological record. It seems to me that Widukind’s “befuddlement” of Hermes and Mars in regards to Irmin strongly suggested an association with the “Marslike Mercury” of the Germanic peoples. Namely, the Marslike Mercury that is the god Woden.
One might also observe that, as one of the noble sons of Mannus, Irmin was — like his elder brother Ingui and the Ingvaeones — a patron of the Irminonic mega-tribal-grouping of the Folk. As such, both sons of Mannus were most likely gods/progenitors of sacral leadership. This latter point is clearly “reflected” in, ie. spun out of, the clear association of their Migration and Viking Age “counter-parts” with kingship; Yngvi-FreyR and his association with the Bernician line of Anglo-Saxon England, the Danes, and the Ynglings of Sweden and Odhinn with … virtually every other kingly house in NW Europe. In contrast, Tiw himself has no direct association with kingship or the founding of kingly lines.
Finally, it is also worth a mention in passing that the Irminonic tribes occupied the interior of Germany, in relation to the seashore dwelling Ingvaeones of southern Scandinavia. According to Snorri Sturlusson, in his preface of the Prose Edda, Woden came first to Germany, and there founded lines of kings before moving up into the Northlands and his meeting with the Yngling-King, Gylfi of Ingvaeonic Sweden; which might well be a mythologization of the evolution of the cult of Woden among the tribes of Germania and the spread of these revised, Roman influenced and Woden centered beliefs, back up into the cradle of Germanicism.