Through MS such as the Codex Argenteus (Uppsala University Library) Gothic is reasonably well documented. Also Crimean Gothic is represented with a list of words by diplomat Busbecq in the sixteenth century.
Goti, Gauti, and Guti and Göta älv (Gautic River) in Sweden – A Few Notes on a Tribal Name
In the ancient world there were different Germanic and non-Germanic peoples like the Vandals, Visigoths, Ostrogoths, Gepids, Rugians, Sciri, and Burgundians. They had a common faith (Arianism) and law, Lex Gothica, and similar languages. The Amal Origo Gothica, however, limited the classification of Goths to a Scandinavian origin (Visigoths, Ostrogoths and Gepids).
The form Gut- (as in Guti) can be found in names like Gota alv, as the river of the Goti is called. Procopius wrote about the Gauts of Thule. The hotly debated question is if the Guti are connected to Gota alv (and Västergotland or West Gothia) or to Östergötland and and the island of Gutland (now named Gotland) in the Baltic Sea or all three.
The Gothic name can be found in several regions in Europe. Connected to for instance (V)andalusia is Gothia-Alania. Vastergotland, Ostergotland and Gutland are however original Gautic-Gothic names.
It has been noted by Piergiuseppe Scardigli (in The Nordic Languages – An International Handbook of the History of the North Germanic Languages, Vol. 1, Berlin/New York 2002, p. 556) that the name of Gutland contains in its first component the people name Goths. The name of the island is athematic, as in Gut- in Guthiuda (dat.).
“There can be no doubt that the identical name for the Goths lies behind both forms. There are two possible explanations for the name of the island. Perhaps the Goths had settled there and a small tribal group emigrated, whose population later greatly increased. Conversely, the Goths could have reached the island at an early time and settled there (see Reinhard Wenskus, Stammesbildung und Verfassung. Das Werden der frühmittelalterliche gentes, Köln/Graz 1961/1977, p. 464 ff.). In both cases these Goths were later assimilated and the Gutnic language became North Germanic.”
The migration of the Goths from South Scandinavia, perhaps the most prominent of the East Germanic peoples is described in Getica (25-27) by Jordanes as a coming forth from Scandza, a hive of races or a womb of nations under their king Berig. When landing on the Polish coast at the mouth of the River Vistula they named the place Gothiscandza. The peoples sailed in three ships, so the myth, of which one was manned by the Gepids, and the two other by Goths.
The general view has been that the migrants came from the provinces of Västergötland and Östergötland on the southern part of the Scandinavian Peninsula or/and the Island of Gotland in the Baltic Sea.
The tribal designation of the gøtar (the inhabitants of the Götaland Region in now South Sweden), is closely related to the designations Goth (gutans) and Old Swedish gutar (Gotlanders), which formally correspond to each other (compare Västergötland, Östergötland and Gotland). It has however not been possible with traditional archaelogical technique either in South Scandinavia or in northern Poland to establish a specific link between Gauts, Gotlanders and Goths.
There are also other possible migrations from South Scandinavia. Vendsyssel, the northern area of the Jutland peninsula, has been regarded as original home of the Vandals, who ended up founding a kingdom in North Africa during the Fifth Century AD. According to History of the Langobards by Paul the Deacon the Lombards originated in Scadinavia (which has been interpreted as Skåne Province (Scania) in southernmost Sweden. Furthermore the Burgundians have been thought to originate on the Island of Bornholm (older name Burgundarholm) in the Baltic Sea. The elusive Eruli (in this case the Eastern Eruli) joined the Goths in the Black Sea area attacking Asia Minor and in the Eastern Mediterranean in the Third Century AD (The World Crisis of the Third Century AD). Part of the people remigrated to Scandinavia to settle near the remaining Gauts according to historian Procopius. There are further examples, but those mentioned above are the most prominent.
In the 1990s a Swedish scholar (Ingemar Nordgren in The Well Spring of the Goths) expressed the view that the names of the Gothic peoples are theophoric and originally seems to be linked with the creator-god Gaut. Gothic ethnicity could thus have been founded on a common cult with its religious origin in southern and southwestern Scandinavia, an area also embracing southern Jutland.
So far scholars have not been able to solve the question of the origin of the Goths and a number of other ancient Germanic peoples. Therefore we could in the future be looking for a solution in the study of ancient DNA.