If there is one deity present in Germanic mythology which can be traced back to Proto-Indo-European times, not just in type as with *Thunaraz but in name then it is *Tiwaz. Although He does not feature prominently in the Eddas we must remember that by the time of the close of the Viking age He had been pushed very much into the background by both *Thunaraz and *Wodanaz who took over many of His original functions. If it were not for etymology we would be much more in the dark about this enigmatic God than we currently are.
"Tyr (ON). The Old Scandinavian name for the Germanic god of the sky, war and council >*Tiwaz (OHG Ziu), who is the only Germanic god who was already important in Indo-European times: Old Indian Dyaus, Greek Zeus, Latin Jupiter, as well as Old Indian deva, Old Irish dia, Latin dei, ON tivar (plural to Tyr) 'gods' are all closely related etymologically to each other." (Dictionary of Northern Mythology, Rudolf Simek)
"But the name of Zeus is not confined to Greeks and Hindus. The Zeus Pater of the former and the Dyaus-pitar of the latter represent the Jupiter of the Latins, and the Tuisco, Zio, Tyr and Tiw of the German nations. The etymological changes of the word are indeed almost numberless. The brightness of the heaven reappears in the Latin dies, the Sanskrit dyu, and our day: and from the same root spring the Greek Theos, the Latin Deus, and the Lithuanian Diewas." (The Mythology of the Aryan Nations Volume 1, George William Cox)
To the Anglo-Saxons *Tiwaz was Tiw or Tig and He is remembered in the 3rd day of the week, Tuesday from the Anglo-Saxon tiwesdaeg or tiswesdag. Each time we say this day we invoke His name. The ON equivalent for Tuesday is tysdagr and the OHG dingesdag, a variant of His name as Thingsus.
"Some of the variations of the names of the various Germanic languages are also of interest. German Dienstag and Dutch dinsdag, 'Tuesday', are based on an adjective thingsus, 'protector of the thing or assembly', used to describe the war god, and this suggests that the predecessor of Tyr had a connection with lawful assembly that is hardly to be seen in the god as we know him." (Handbook of Norse Mythology, John Lindow)
He was equated with the Roman God Mars as He became relegated to being a war God from His once lofty position as supreme deity of both the Germanic and Aryan peoples. *Thunaraz and *Tiwaz are in fact older deities than *Wodanaz but the Eddas relegate both of these Gods to being sons of Odin. Thus the role and nature of *Wodanaz may have been much different from the Odin that is left to us in the rather late Eddas.
"We see that Tyr has lost most of the glory implied by the etymology of his name, which derives from the same Indo-European root as the names of Zeus and Jupiter and of our word 'deity' (compare Latis deus), his predecessor may once have been a far greater warrior than Tyr seems to be in the extant mythology.We surmise that the original Odin is seen in his fickle and cunning aspects, not in his role as lord of hosts and ruler of the pantheon. Similarly, we surmise that the predecessor of Thor might possibly once have been the head of the pantheon, and that the predecessor of Frigg may once have been inspired love the way Freyja does in the texts that have come down to us." (Lindow)
The eclipse of the glory of this ancient God is emphasised in Jaan Puhvel's Comparative Mythology:
"In Scandinavia he is a sunken god in the heyday of the Odinic death cult, but his intrinsic eminence is not in question; witness the lingering importance of the Continental Tiw-Saxnot (in a ninth century Old Saxon baptismal vow the convert renounces allegiance to Thunaer, Woden, and Saxnote).
Puhvel draws a comparison with the Irish Nuada who like *Tiwaz was once the leader of the Celtic family of Gods until eclipsed by Lugh, the equivalent of *Wodanaz:
"The ascendancy of Lug over Nuada parallels the eclipsing of Tyr by Odin in Norse tradition."
Like Tyr, Nuada also lost His arm but it was later replaced by a false silver one:
"Their king was Nuada, who lost his arm in the battle against the Fir Bolg." (Puhvel)
After the fitting of His silver arm He became known as Nuada Argatlam (Nuada of the Silver Hand). Shortly after this Nuada loses his sovereignity over the Tuatha De Danann to Lugh. It is conjectured that the reason for this is that He became blemished due to His physical maiming.
In previous articles I have speculated that the God who the Semnones worshipped in their sacred central grove was none other than *Tiwaz. They were also called Ziuwari. Ziu is remembered in many place names and mountain names in Germany and Switzerland. Even plants were named after Him:
"The names of plants also confess the god: ON. Tysfiola, I dare say after the Lat. viola Martis, march-violet; Tyrhialm (aconitum), otherwise Thorhialm, Thorhat (helmet, hat), conf. Germ. sturmhut, eisenhut, Dan. troldhat, a herb endowed with magic power, whose helmet-like shape might suggest either of those warlike gods Tyr and Thorr; Tyvidr, Ty's wood, Dan. Tyved, Tysved (daphne mezereum), in the Helsing. dial. tis, tistbast, the mezereon, a beautiful poison flower." ( Teutonic Mythology Volume 1, Jacob Grimm)
Grimm also points out that the rune Tiwaz is the only rune which specifically names a Germanic deity:
"How comes it that no rune has taken its name from Wuotan or Odinn, the inventor of writing itself? 'R=reid, rad, ' i.e., waggon, may indirectly at least be referred to the god of the Thunder-car; and F according to one interpretation signifies Freyr. Anyhow, T=Tyr appears to have been a supremely honoured symbol, and the name of this god to have been specially sacred: in scratching the runes of victory on the sword, the name of Tyr had to be twice inserted, Saem. 194b. The shape of the rune ᛏ has an obvious resemblance to the old-established symbol of the planet Mars when set upright ♂ , and an AS. poem on the runes expressly says: tir bid tacna sum (tir is one of the tokens, is a certain sign); where again the derivative form tir is employed to explain the simple Tiw or Ti."
Interestingly Grimm goes on to analyse the Anglo-Saxon Ear rune ᛠ which does resemble the Tir rune. This rune is the final rune of the Anglo-Saxon Futhork but the 29th rune of the 33 rune Northumbrian Futhork. It is taken to signify the grave, dust. However Gimm associates this rune with Tyr/Tiw/Zio and discusses how its name Ear is linked to the Irminsul:
"Evidence as regards Low Germany is found both in the rune Ear occurring in Anglo-Saxon, and in the remarkable name of Eresburg, Aeresburg being given to a notable seat of pagan worship in a district of Westphalia, in the immediate neighbourhood of the Irminsul (v. supra, p 116). That it was strictly Eresberg (as Siegburg was originally Sigberg, p. 198), follows both from the Latin rendering mons Martis, and from its later name Mersberg, whose initial M could be explained by the contraction of the words 'in dem Eresberge, Aresberge', or it may be an imitation of the Latin name. There was a downright Marsberg in another district of Westphalia. This Eresberc then is a Ziesberc, a Sig-tiwes-berg, and yet more closely an Arreopagus, Mars' hill."
This association between *Tiwaz and Irmin (the high God of the Arya, know also as Eremon, Aryaman, Airyaman and Ariomanus amongst the various Aryan peoples) is further demonstrated in the names of the days of the week amongst High German tribes:
"Still more plainly are High German races, especially the Bavarian (Marcomannic) pointed to by that singular name for the third day of the week, Ertag, Iertag, Irtag, Eritag, Erchtag, Erichtag, which answers to the rune Eor, and up to this moment lives to part off the Bavarians, Austrians and Tyrolese from the Swabians and Swiss (who, as former Ziowari, stick to Ziestag); along the boundary line of these races must also have run formerly the frontier between Eor-worship and Zio-worship.
Grimm then goes on to make the bold claim that Eor, who is presumably Irmin is to be regarded as the son of Zio:
" As Zio is identical with Zeus as director of wars, we see at a glance that Eor, Er, Ear, is one with Ares the son of Zeus; and as the Germans had given the rank of Zeus to their Wotan, Tyr and consequently Eor appears as the son of the highest god."
In a previous article I have discussed how the Cheruscans were named after a God Cheru or Heru, a sword God who is none other than Saxnot. http://celto-germanic.blogspot.co.uk/2014/02/heru-god-of-cherusci.html
"Another naked sword flashes on the wooded heights in the land of the Cherusci; it is the weapon of the sword-god Heru, Cheru or Saxnot, who some think is no other than Tyr. Of this weapon Saga tells us that it causes the destruction of its possessor, should he be unworthy of owning it; but that in the hand of a hero it brings victory and sovereignty."(Asgard and the Gods, Wilhelm Waegner, 1886)
The great legendary hero of the Cherusci was Arminius or Hermann who although historical was in my opinion an Avatar of Irmin sent to rescue and to unite the German Volk. Grimm makes the same connection between the Cherusci and Cheru/Heru:
"The AS. genealogies preserve the name of Saxneat as the son of Woden, and it is in perfect accordance with it, that Tyr was the son of Odinn, and Ares the son of Zeus (see Suppl.). But further, as the Saxons were so called, either because they wielded the sword of stone (saxum), or placed this god at the head of their race, so I think the Cheruscans of Tacitus, a people synonymous, nay identical with them, were named Cheru, Heru=Eor, from whom their name can be derived."
He even draws a connection with the Gallic deity Esus:
"After this weighty consonance of facts, which open to us the meaning of the old national name, and at the same time teaches us that 'heru' was first of all pronounced 'cheru', and last of all 'eru, er', I think we may also bring in the Gallic war-god Hesus or Esus (Lucan 1 ,440), and state, that the metal iron is indicated by the planetary sign of Mars, the AS. 'tires tacen', and consequently that the name Zio and Eor may be the picture of a sword with its handle, or of a spear. The Scythian and Alanic legends dwell still more emphatically on the god's sword, and their agreement with Teutonic ways of thinking may safely be assumed, as Mars was equally prominent in the faith of the Scythians and that of the Goths.
"The impressive personification of the sword matches well with that of the hammer, and to my way of thinking each confirms the other. Both idea and name of two of the greatest gods pass over into the instrument by which they display their might.
"Herodotis 4, 62 informs us, that the Scythians worshipped Ares under the semblance or symbol of an ancient iron sword, which was elevated on an enormous stack of brushwood ['three furlongs in length and breadth, but less in height'].
Tyr has become a general name for God and examples such as Hangatyr (God of the Hanged) and Hertyr (God of Armies) exist as Odinsheiti or bynames for Odin. This is just another example of how ancient and revered the name of Tyr is.