The name of Sweden was originally a plural form of Swede and is a so-called "back-formation", from Old EnglishSweoðeod, which meant "people of the Swedes" (Old NorseSvíþjóð, LatinSuetidi). This word is derived from Sweon/Sweonas (Old NorseSviar, LatinSuiones). As the name for the country itself, Sweden is borrowed from DutchZweden, which is probably the dative case of Zwede. It appeared in Scots during the 17th century in forms such as Swethin and Swadne. Before this, Sweden was called Swedeland, and in Old English it was called Sweoland (see Svealand) or Sweorice (Old NorseSviariki, which is an older form of the modern Swedish name for the country, Sverige).
In Sweden, the form Swerike is attested from the end of the 13th century, Svearike, from the 14th century, as well as the Icelandic Svíaríki and the Old GutnishSuiariki. In those days the meaning was restricted to the older Swedish region in Svealand and did not always include Götaland, the land of the Geats. The word rike, meaning realm or kingdom, is the same as Danish rige and German Reich and also appears in the name of the legislature, Riksdag, Danish rigsdag, German Reichstag.
Towards the end of the 15th century, the form had changed to Swerighe both in Swedish and Danish, like bakare ("baker") to bagare and mik ("me") to mig. Finally in the 17th century, forms such as Swerghe and Swirghe appeared. Gustavus Adolphus used the form Swirge.
Today, the pronunciation has changed the form further and it is pronounced [ˈsvær.jə] in modern Swedish, while the late medieval form Sverige is used in writing.
Much is made about the difference between the medieval forms Svearike and Sverige. Although, medieval Swedes were unlikely to see it as anything else but a matter of pronunciation. There is, however, an alternative hypothesis, first proposed by Ivar Modéer, and later popularized by the Swedish author Jan Guillou that the form is a loan from the Danish form of Sverike (Svearige). The objective is to separate the two forms as two different concepts, and today Svea Rike has formal connotations, and may even be used to treat Iron Age-Medieval Sveariket (always in definite form) as a different nation from the later Sverige.
Notably, a naming that stems from a completely different root is the one used in some Finnic languages, in FinnishRuotsi, in EstonianRootsi, probably derived from various uses of rōþs-, i.e., "related to rowing" in Old Swedish, cf. Rus.