Goths were an East Germanic tribe which according to their own traditions originated in Scandinavia (specifically Götaland and Gotland). They migrated southwards and conquered parts of the Roman empire. Two closely related tribes that remained in Scandinavia and who are often The Gn called Goths are separately treated, as Geats and Gotlanders.
History
Our only source for early Gothic history is Jordanes' Getica, (published 551), a condensation of the lost twelve-volume history of the Goths written in Italy by Cassiodorus. Jordanes may not even have had the work at hand to consult from, and this early information should be treated with the highest degree of caution. Cassiodorus was well placed to write of Goths, for he was an essential minister of Theodoric the Great, who apparently had heard some of the Gothic songs that told of their traditional origins, related in turn by Jordanes with the remark "for so the story is generally told in their early songs, in almost historic fashion." The Gothic bards accompanied themselves on a stringed instrument that Latin writers associated with the cithara, which was more familiar to them.

They were settled for some time in the Vistula Basin (called Gothiscandza by Jordanes), from where they migrated towards the south-east. They battled with, and temporarily subjugated, the ancestors of the Slavs (there were many Gothic loanwords in proto-Slavic), who lived between the Baltic Sea and the Black Sea and ultimately settled in 'Scythia' a vast undefined region that includes modern Ukraine and Belarus (called Oium by Jordanes). A united tribe until the third century, it was during that period that they split into the eastern Goths or Ostrogoths and the western Goths or Visigoths.

Though many of the fighting nomads who followed them were to prove more bloody, the Goths were feared because the captives they took in battle were sacrificed to their god of war, Tyz [1] (http://www.northvegr.org/lore/grimmst/009_03.php)(the one-armed Tyr), and the captured arms hung in trees as a token-offering. Their kings and priests came from a separate aristocracy, according to Cassiodorus/Jordanes, and their mythic kings of ancient times were honored as gods. Their mythic lawgiver, named Dicineus, traditionally dated about the 1st century BC, ordered their laws, which they possessed by the 6th century in written form and called belagines.

A force of Goths launched one of the first major "barbarian" invasions of the Roman Empire in 267. A year later, they suffered a devastating defeat at the Battle of Naissus and were driven back across the Danube River by 271. This group then settled on the other side of the Danube from Roman territory and established an independent kingdom centered on the abandoned Roman province of Dacia, as the Visigoths. In the meantime, the Goths still in Ukraine established a vast and powerful kingdom along the Black Sea. This group became known as the Ostrogoths.

The Goths were briefly reunited under one crown in the early sixth century under the Ostrogothic king Theodoric the Great, who became regent of the Visigothic kingdom for nearly two decades.

For the later history of the Goths, see Visigoths and Ostrogoths.

Origins
After having introduced Scandinavia and its nations (for a discussion, see Scandza), Jordanes recounted:

Now from this island of Scandza, as from a hive of races or a womb of nations, the Goths are said to have come forth long ago under their king, Berig by name. As soon as they disembarked from their ships and set foot on the land, they straightway gave their name to the place. And even to-day it is said to be called Gothiscandza.
This account has been discussed for a long time. Although no alternative theory has been proposed for the appearance of Germanic tribes in northern Poland, some historians, such as Heather, doubt that the Goths originated in Scandinavia. This is due to the fact that, disregarding Jordanes, the earliest literary evidence for the Goths (Tacitus and Ptolemy) puts them at the Vistula in 1st century AD. However, besides Jordanes' account, there is both linguistic and archaeological support for the Scandinavian origin.

Archaeology
In Poland, the material culture associated with these Goths (or better Gotones) is typically identified with the Wielbark/Willenberg culture[2] (http://www.muzarp.poznan.pl/archweb/gazociag/title5.htm). During the late Nordic Bronze Age and early Pre-Roman Iron Age (ca 600 BC - ca 300 BC), this area had strong influences from southern Scandinavia, which made the Wielbark culture closely related to that of southern Sweden[3] (http://www.arkeologi.uu.se/publications/opia/gothicabstract.htm). During this period the warm and dry climate of southern Scandinavia (2-3 degrees warmer than today) deteriorated considerably, which not only dramatically changed the flora, but forced people to change their way of living and to leave settlements. The Goths are believed to have crossed the Baltic Sea towards the end of this period, ca 300 BC and later. In the traditional province of Ostrogothia, in Sweden, there appears to have been a general depopulation during this period. Modern archaeological research consequently supports the Scandinavian origin of the Goths and the authenticity of their tradition.

However, the Gothic culture also appears to have had continuity from earlier cultures in the area, suggesting that the immigrants mixed with earlier populations, perhaps providing their separate aristocracy. This scenario would make their migration accross the Baltic similar to many other population movements in history. This culture shifted south-eastwards towards the Black Sea area from the mid-2nd century. There, they appear to have imposed themselves as the rulers of the local, probably Slavic, Chernyakhov Culture (ca 200 - ca 400).

There is archaeological and historical evidence of continued contacts between the Goths and the Scandinavians during their migrations.

Linguistics
There are close linguistic connections between Gothic and Old Norse (see East Germanic languages and Gothic). Moreover, there were two closely related tribes that remained in Scandinavia, the Geats and the Gotlanders, and these tribes were considered to be Goths by Jordanes (see Scandza).

The word "Geats" (Anglo-Saxon Geatas) and the Swedish word "Götar" (East Norse Gøtar) both represent the expected outcome of proto-Germanic *Gauta-. This form is related to the reconstructed root *Gut- which seems to be the origin of "Goth," which appears earliest in forms such as "Gutthones" in Greek ethnography.

Philologists have reconstructed *Gut-þiuda, the "Gothic people," as a likely original form of the name. This form also appears in the Gothic Calendar (aikklesjons fullaizos ana gutþiudai gabrannidai). Besides the Goths, this way of naming a tribe is only found in Sweden (see Suiones and Suiþioð).

The reconstructed root *Gut- is identical to that of Gotland, an island in the Baltic Sea, and in older scholarship the dialect of Gotland was regarded as a form of Gothic. The most famous example is that both Gutnish and Gothic used the word lamb for both young and adult sheep. Still, some claim that Gutnish is not closer to Gothic than any other Germanic dialect. Interestingly, the Gotlanders (Gutar) had oral traditions of a mass migration towards southern Europe written down in the Gutasaga.