In about 222 BCE, the first use of the Latin term "Germani" appears in the Fasti Capitolini inscription de Galleis Insvbribvs et Germ(aneis). This may simply be referring to Gaul or related people; but this may be an inaccurate date since the inscription was erected in about 18 BCE despite referencing an earlier date. The term Germani shows up again, allegedly written by Poseidonios (from 80 BCE), but is merely a quotation inserted by the author Athenaios who wrote much later (around 190 CE). Somewhat later, the first surviving detailed discussions of Germani and Germania are those of Julius Caesar, whose memoirs are based on first-hand experience.
From Caesar's perspective, Germania was a geographical area of land on the east bank of the Rhine opposite Gaul, which Caesar left outside direct Roman control. This word provides the etymological origin of the modern concept of "Germanic" languages and Germany as a geographical abstraction. For some classical authors Germania also included regions of Sarmatia, as well as an area under Roman control on the west bank of the Rhine. Additionally, in the south there were Celtic peoples still living east of the Rhine and north of the Alps. Caesar, Tacitus and others noted differences of culture which could be found on the east of the Rhine. But the theme of all these cultural references was that this was a wild and dangerous region, less civilized than Gaul, a place that required additional military vigilance.
Caesar also used the term Germani for a very specific tribal grouping in northeastern Belgic Gaul, west of the Rhine, the largest part of whom were the Eburones. He made clear that he was using the name in the local sense. These are the so-called Germani Cisrhenani, whom Caesar believed to be closely related to the peoples east of the Rhine, and descended from immigrants into Gaul. Tacitus suggests that this was the original meaning of the word "Germani" – as the name of a single tribal nation west of the Rhine, ancestral to the Tungri (who lived in the same area as the earlier Germani reported by Caesar), and not the name of a whole race (gens) as it came to mean. However, Tacitus adds that in due time, the name Germani "gradually acquired a wider usage" and that "once they had got to know the name, they all called themselves Germani." Caesar described this group of tribes both as Belgic Gauls and as Germani. Gauls are associated with Celtic languages, and the term Germani is associated with Germanic languages, but Caesar did not discuss languages in detail (though he did say that Belgic Gaul was different from Celtic Gaul in language). The geographer Ptolemy described the place where these people lived as Germania, which according to his accounts was bordered by the Rhine, Vistula and Danube Rivers, but he also circumscribed into Greater Germania an area which included Jutland (Cimbrian peninsula) and an enormous island known as Scandia (the Scandinavian peninsula).
While saying that the Germani had ancestry across the Rhine, Caesar did not describe these tribes as recent immigrants, saying that they had defended themselves some generations earlier from the invading Cimbri and Teutones. (He thereby distinguished them from the neighbouring Aduatuci, whom he did not call Germani, but who were descended from those Cimbri and Teutones.) It has been claimed, for example by Maurits Gysseling, that the place names of this region show evidence of an early presence of Germanic languages, as early as the 2nd century BCE. The Celtic culture and language were however clearly influential also, as can be seen in the tribal name of the Eburones, their kings' names, Ambiorix and Cativolcus, and also the material culture of the region.[b]
The etymology of the word Germani is uncertain. The likeliest theory so far proposed is that it comes from a Gaulish compound of *ger "near" + *mani "men", comparable to Welsh ger "near" (prep.), Old Irish gair "neighbor", Irish gar- (prefix) "near", garach "neighborly". Another Celtic possibility is that the name meant "noisy"; cf. Breton/Cornish garm "shout", Irish gairm "call". However, here the vowel does not match, nor does the vowel length (contrast with inscriptional Garmangabi (UK) and Garma Alise, G-257)). Others have proposed a Germanic etymology *gēr-manni, "spear men", cf. Middle Dutch ghere, Old High German Ger, Old Norse geirr. However, the form gēr (from PGmc *gaizaz) seems far too advanced phonetically for the 1st century, has a long vowel where a short one is expected, and the Latin form has a simplex -n-, not a geminate.
The term Germani, therefore, probably applied to a small group of tribes in northeastern Gaul who may or may not have spoken a Germanic language, and whose links to Germania are unclear. It appears that the Germanic tribes did not have a word to describe themselves, although the word Suebi, used by Caesar to broadly classify Germanic speakers, was likely Germanic in origin.[c] They did however use the term walhaz to describe outsiders (mainly Celts, Romans and Greeks). Roman authors frequently employed the term "barbarian" from the Latin derivative barbarus (inherited from the Greek barbaros which means "foreign") when describing Germanic peoples. Such a term presupposed a distinctive Roman intellectual and cultural superiority and their ethnographic treatises on the various barbarian tribes ascribed specific attributes of barbarism to each one so as to delineate the dichotomy between barbarism and civilization. The more the Romans increased their presence along the periphery of their Empire, the more trade and employment for the barbarians became available, resulting in an economic boom along the corridors of the Danube River, which subsequently increased the Roman focus upon the Germanic peoples. Use of the modern term German or Germanic is the result of 18th and 19th century classical philology which "envisioned the Germanic language group as occupying a central branch of the Indo-European language tree."
Latin scholars of the 10th century used the adjective teutonicus (a derivative of Teutones) when referencing East Francia, which in their vernacular was connoted "Regnum Teutonicum", for that area and all of its subsequent inhabitants. Modern speakers of English still use the word "Teutons" to describe Germanic peoples. Historically, the Teutones were only one specific tribe, and may not even have spoken a Germanic language. For example, some scholars postulate that the original Teutonic language may have been a form of Celtic. The source of this confusion, whereby Teutons are lumped into the same category as German-speaking tribes, comes from their contact with the Romans in the 2nd century BCE, when they, along with the Cimbri and the Ambrones, led a frightening attack against the Romans. Teuton was the byword the Romans applied to the barbarians from the north and which they used to describe subsequent Germanic peoples. Under the leadership of Gaius Marius, who built his career on barbarian antagonists (like many who followed), the Teutones became one of the archetypal enemies of the Roman Republic.