According to Professor Jean Haudry the term ari means 'tribe' (see p.59, The Indo-Europeans). Indeed he draws a link between this root word and the name of the pan-Aryan God Aryaman:
"For the Aryans this national community, called ari-'tribe', was symbolized and embodied in an entity called in Vedic Aryaman-('Aryanhood' (Puhvel 1978: 336), cf. Dumezil 1949; 'Aryan name' i.e. 'Aryan people', Haudry 1990c). Aryaman presides over all relations which outsteps the limits of the clan, the host-guest relationship for example, but also marriage and what might be called the general good; he is as well the god of roads. All of this is outside the sphere of the clan but as a whole remains within the tribal (national) framework. It is the king who most has the duty of respecting and embodying the bond symbolized by Aryaman; 'father of the people', he belongs by birth to what has the most right to be called the nucleus of the community." (page 59)
"The ari- (together with its personification, the god Aryaman) denotes also the tribe or the confederation of tribes which make up the 'nation'; but at the same time it denotes the Aryan national community as distinct from the non-Aryans: moreover ari- signifies a person not belonging to the family, the village or the clan." (page 43)
The Aryan Indian God Aryaman, derived from the PIE *aryo-mn is thus the divine embodiment of the entire Aryan community on a national level, not merely a local one and His cognates may be found in other parts of the Aryan world, such as Iran (airyaman), Gaul (Ariomanus), Ireland (Eremon) and Germany (Irmin):
"Aryan god (*h4eros). A deity in charge of welfare is indicated by a number of lexical correspondences (Skt Aryaman, Av airyaman, Gaul Ariomanus, OIr Eremon,.." (p 433 The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World, J.P. Mallory and D.Q. Adams)
Whilst Mallory and Adams insist that "there is no evidence that the speakers of the proto-language referred to themselves explicitly as 'Aryans'." (p 266), this argument holds no water in my opinion when one considers that both scholars appear to accept that the term 'Arya' is derived from the PIE *h4eros and thus WAS in the lexicon of our Proto-Indo-European ancestors but it is not popular, politically correct or conducive to the furtherance of the careers of 21st century academics to admit this obvious fact.
Mallory and Adams state that *h4eros means 'member of one's own group'. This term is also found not only amongst the Indians and Iranians but also amongst the Hittites-ara-'member of one's own group, peer, friend'. The Anatolian Lycian arus means 'citizens' and the Old Irish aire-'freeman'. Despite the evidence from various Indo-European languages and the belief that "The evidence suggests that the word was, at least initially, one that denoted one who belongs to the community in contrast to an outsider;" (page 266) there is continuing denial by academics that the term was used as a self-descriptor by the Proto-Indo-Europeans. The evidence from Ireland is particularly compelling when one considers that Ireland is the furthest west from India and Iran and thus demonstrates a lexical continuum over thousands of miles. 'Arya', is reflected in 'Ireland', 'Erin', 'Eire' as well as the term 'aire' and the Goddess name 'Eriu'.
The aforementioned two scholars however do not refer to the Germanic link. I don't know if this is due to a lack of knowledge or perhaps a denial of the link but one certainly exists in the name of the Germanic God Irmin. Just as the root word ari- signifies the 'tribe' or 'national community', the term Irmintheod (OS 'mankind') is derived from Irmin.
One scholar however does recognise this Germanic link-Puhvel:
"There is more congruence between *Tiwz and *Wodanaz and the Vedic Mitra-Varuna pair as the benevolent contractual patron coupled with the devious and sinister binder-god. There may even be a Germanic parallel to Mitra: Aryaman (and Nuada: Eremon in chap 10) in the Saxon coexistence of Saxnot and Irmin (a god whose name occurs in Irminsul, the cultic pillar razed by Charlemagne, and in Old Saxon Irmintheod 'mankind', literally 'Irmin's people'; cf. aryaman-in chap. 4)." (Comparative Mythology)
There is thus not only a lexical but a mythological continuum between Ireland in the far west and Iran-India in the farthest east with respect to the root word ari-. Another scholar whose work I follow and admire is Alexander Jacob. He speculates that the Germanic tribal confederation Alemanni may be a corruption of an earlier form of the word Aryamanni (page 162, The Two Grails). This would draw a direct link between the Indo-Iranian terminology and the Germanic. He also briefly remarks that "the Germanic tribes may have formed a part of the northern Cimmerian Celtic race,", an exceedingly ancient Aryan people who he believes to have settled in the British Isles and Gaul, the original Druids being their priestly caste. The Alemanni my readers may recall are descended from the Herminones who I conjecture were named after their ancestral deity Irmin who is one of the Indo-European deities cognate with *aryo-mn."The king of the Sons of Mil, Eremon, is etymologically the equivalent of the Gaulish Ariomanus, reflecting the same personified *aryomn 'Aryanness' as is seen in the Vedic Aryaman and the Iranian Airyaman. In addition, very specific traits connect Eremon with both of the latter. The dossier of Eremon in the Lebor Gabala involves his role as builder of causeways and royal roads. In the Historia Britonum of Nennius, the Book of Leinster, the Book of Lecan, and some other scources, Eremon arranged a protection against poisoned enemy arrows that consisted of pouring cow's milk into furrows on the battlefield. He also provided wives to his allies and arranged for hereditary succession in favour of the Irish, his own people."
The very fact that Indo-European peoples as widely dispersed as the Teutons, Irish, Gauls, Iranians and Indo-Aryans should have a common deity from which we get the term Arya is in itself sufficient evidence for the original common origins of these peoples. The realisation that the Germans should, like the Iranians and Indo-Aryans call themselves Arya is further compelling evidence that this is a term which belongs not just to the Indo-Iranians but other Indo-Europeans. It is also interesting to note that the Alemanni is a term used of the entire German folk by the French, Allemands. The Alamanni, the Germans are thus the Aryan men.
If the root word ari- means 'tribe', 'people', 'national community' which I feel that I have demonstrated here that it does then we also have a link in type with the Germano-Celtic term teut which essentially means the same thing and from this we get the word Teuton. The name Teutoburg could be interpreted as the fortress of Teut. Now Teut is cognate with the Old English theod (Proto-Germanic *theudo) and the Irish Tuatha (Proto-Celtic *touta) demonstrating an early Celto-Germanic shared word but it has an even earlier PIE root: *teuta. However Teut was also the eponymous deity of the Teutonic peoples. Teut may be derived from Tuisco, referred to in Tacitus' Germania, the father of Mannus and the grandfather of the Ingvaeones, Herminones and Istaevones. He is the ancestral God of the Germanic or Teutonic peoples and He is thus honoured in the place name Teutoburg. How fitting that the Teutoburg should be the scene of Germania's triumph and Rome's defeat! From Teut we derive the name by which we call ourselves-Teutons which is cognate with Deutsch. So Deutschland is the land of the Teutons. The Tuatha De Danann, a mysterious and divine Nordic race who according to the Lebor Gabala Errren (The Book of the Taking of Ireland) are the Aesir of Germanic mythology in a different cultural setting and many of the Irish deities have direct counterparts in Germanic mythology.
Tuath in Old Irish likewise means 'people', 'tribe', 'nation'. Some scholars speculate whether the tribe known as the Teutones from where we derive the term Teuton was a Celtic or a Germanic one. Their original homeland was in Jutland in Scandinavia which strengthens the argument that they were Teutonic. However this in itself is not conclusive evidence as the Celts and Teutons did live close to one another and frequently exchanged territory as the result of conquest and/or migration. Gudmund Schuette in Our Forefathers the Gothonic Nations. A Manual of the Ethnography of the Gothic, German, Dutch, Anglo-Saxon, Frisian and Scandinavian Peoples Volume 1 refers to the Teutons as "comrades of the Cimbri", "the Germans" and "the entire body of our forefathers." (page 36). This is generally how they are viewed. He also confirms the link between Teuton and Deutscher:
"Teutons = 'Inhabitants of Thiuth.'
This academic expression used by German, French and English scholars really goes back to the Teutonic companions of the Cimbri who probably came from Denmark. The similarity of the name 'Teuton' to the form 'teutsche', i.e. 'German', is in essence responsible for its general use;" (page 12)
"Teutons, literally = 'people', later = 'Germans'.
The root = 'people' is the same as in 'Deutsche, Teutsche' and therefore 'Teutons' is often used as a Latinisation of this name. There is, however, no direct historical connexion as the Teutons undoubtedly lived outside of Germany, most probably in the district of Thiuth on Zealand, perhaps also in the Jutland Thiuth, now Ty." (page 29)
He considers Teutsche and Theutonici to be intermediate forms of Teutons. In addition to the link between Teuton and Tuatha there is a further Celtic link via the name of a Gaullish deity, Teutates who usually appears in Classic writings in the company of two other Gods, Taranis, a thunder deity, and Esus.
"Teutates (Toutates, Totates, Tutates) is derived from *tewta 'people' (Old Irish tuath, Oscan touto, Gothic thiuda)...." (Comparative Mythology)
Because of the etymology of Teutates it is assumed by scholars that He was a tribal protector God. His cult was popular in both Gaul and Britain and He was considered by the Romans to be the Celtic equivalent of their Mercury. However frequently the Romans prefixed the name of Mars to form the name Mars-Teutates on monument inscriptions. It is speculated by some scholars (e.g. Miranda Green, The Gods of the Celts) that Teutates was a descriptor of a God's function within a particular tribe rather than the personal name of a specific deity.