Oium was a name for Scythia, or a fertile part of it, roughly in modern Ukraine, where the Goths, under a legendary KingFilimer, settled after leaving Gothiscandza, according to the Getica by Jordanes, written around 551. Whether the story reproduced by Jordanes contains factual information, and if so which parts, is no longer possible to ascertain with any certainty.
Name etymology
Jordanes does not give an etymology, but many scholars interpret this word as a dative plural to the widespread Germanic words or *auwō- and means "well-watered meadow" or "island". The word is believed to be related to older words for water, including Gothicahwa Latin aqua, ultimately a well-attested Proto Indoeuropean root. This is seen as consistent with the description Jordanes gave of the Goths delight in this region's fertility. As mentioned for example by Dennis H. Green Jordanes describes another place with a similar name — the place where the Goths' relatives the Gepids lived:
Chronology
A problem with Jordanes' account is that he dates the arrival of the Goths in Oium well before 1000 BCE. Historians who accept Jordanes' account as partially reflecting real events, do not accept this aspect.
Jordanes
Mierow's translation of the one short passage in Getica IV, which mentions Oium is as follows: The place where they first arrived is thus described not as the whole of Scythia, which Jordanes describes in the subsequent chapter, but a remote and isolated part of it, where the Spali lived. The Goths coming from the Baltic crossed a bridge to get there, but when it broke, it became impossible to cross back and forth anymore. Returning to his narrative, Jordanes described the area where Filimer subsequently moved his people and settled as being near the Sea of Azov, noting that there are verbal legends around about Gothic origins, but that he prefers to trust what he reads: According to Jordanes, the Goths left Oium in a second migration to Moesia, Dacia and Thrace, but they eventually returned, settling north of the Black Sea. Upon their return, they were divided under two ruling dynasties. The Visigoths were ruled by the Balþi and the Ostrogoths by the Amali.
The identified places
Jordanes himself understands Oium to be near the Sea of Azov, which was understood to be a marshy area in this period. Wolfram for example interprets Jordanes in a straightforward way to be referring to a place on the shore of the Sea of Azov. The Reallexikon der germanischen Altertumskunde article on Oium, for example, proposes, based upon a proposal by Herwig Wolfram, that the uncrossable river with a broken bridge might be the Dnieper. The bridge story itself can not be taken literally as bridges crossing major rivers were not known in this area more than 1000 years BCE. It can therefore only refer to events in a much later period. Both Herwig Wolfram and Walter Goffart see the bridge story as likely to be symbolic. Based upon a proposal by Norbert Wagner, the RGA suggests that the marshes surrounding Oium could be the Pripyat or Rokitno marshes in the are of the modern border of Belarus and Ukraine. This is to the west of the Dnieper, and not near Southern Russia where Wagner believed Oium was, and so Wagner saw this area, which contains the Pripyat River, as representing the "river" which needed to be crossed en route to Oium.
Jordanes' sources
As explained above, Jordanes represented his story as being consistent with history-like Gothic songs, and the lost work of Ablabius. He also specifically expressed his preference for written sources in defending this Oium account against legends he had encountered in Constantinople. Concerning the larger work where this story appears, the Getica, Jordanes also explained in his prefaces to it and his other surviving work, the Romana, that he had started the work with the aim of summarizing a far larger work written by Cassiodorus, which has not survived. According to some historians, Jordanes' account of the Goths' history in Oium was constructed from his reading of earlier classical accounts and from oral tradition. According to other historians, Jordanes' narrative has little relation to Cassiodorus's, no relation to oral traditions and little relation to actual history.
Archaeology
Historians such as Peter Heather, Walter Goffart, Patrick Geary, A. S. Christensen and Michael Kulikowski have criticized the use of the Getica as a source for details about real Gothic origins. Archaeologically, the Chernyakhov culture, which is also called the Sântana de Mureș culture, contained parts of Ukraine, Moldova and Romania and corresponds with the extent of Gothic-influenced Scythia as known from 3rd and 4th century contemporaries. For archaeologists who subscribe to the proposal that Jordanes' account of migration from the Vistula can be seen in archaeological evidence, the Vistula archaeological culture which is proposed to represent the earlier Goths is the Wielbark culture. The account of Jordanes fits with the interpretation of the Wielbark and Chernyakhov cultures, in which Germanic peoples from the Vistula Basin, moved towards, influenced, and began to culturally dominate, peoples in the Ukraine. Some of the historians who agree with this scenario, such as Herwig Wolfram, propose that this did not require significant amounts of people to move.
Norse mythology
In The origin of Rus', Omeljan Pritsak connects the Hervarar saga with its account of Gothic legendary history and of battles with the Huns, with historical place names in Ukraine from 150 to 450 AD, This places the Goths' capital Árheimar, on the riverDniepr. The connection to Oium was made by both Heinzel and Schütte. However the attribution of places, people, and events in the saga is confused and uncertain, with multiple scholarly views on who, where, and what real things the legend refers to.