Grimm says (Deutsche Mythol. p. 328, 2nd edit.):  "Die Sachsen scheinen in Hirmin einen kriegerisch dargestellten Wôdan verehrt zu haben."  In fact Irmin, Armin, Eorman, Hermann is the oldest deity of our race.  He is the Er or Eor of the Scythic tribes and the Ares of the Greeks.  He combines the functions of the two later divinities Tiv or Ziv or Ziu, who corresponds to Mars, and Wôdan, who represents Mercury.  And the Irman-sul or pillar of Irman was so common an object that it suggested a designation for any perpendicular object, ever a road running due north (Cambridge Essays, 1856, p. 68).  That the root min in Her-min-ius may be identical with the man of Ir-man might be inferred from ho-min-, ne-min- compared with mann. (Varronianus, Donaldson, 1860)

... Eormon, in the Anglian of Beowulf, means universal; eormoncyn, the whole of mankind; in old Norse, jormün is the world, and Jormungandr is another name of the Midgard snake which encircles the world.  Most likely, the Irmansul thus signified the universal column, the pillar adored by all men; just as the Anglo-Saxons called the great Roman road Eormenstreot, or Ermingstreet, the public road.  Er, then, would be the divinity, man the human word, and Erman would thus express something revered by all; and thence, the name of the tribes of the Hermiones and Hermunduri, both meaning all the people.  Later, the word jormün, or eorman, came to mean only very large; and, probably, the Saxons of Thuringia had forgotten the original signification of their columns when they gave the single one of Irmansul such an exclusive prominence.  Some have tried to explain one pillar as Heermansaul, pillar of the army man; and the other as Raginholdsaul, pillar of firm judgment, as emblems of military and civil power; but though this meaning may have later been bestowed on them, the signification of Eormon is decidedly adverse to this explanation, and it is safest to translate it, when it occurs in names, as public, or general... (History of Christian Names, Yonge, 1884)