The Balts or Baltic peoples (baltai, balti) are an ethno-linguistic group of peoples who speak the Baltic languages of the Balto-Slavic branch of the Indo-European languages.
One of the features of Baltic languages is the number of conservative or archaic features retained. Among the Baltic peoples are modern-day Lithuanians and Latvians (including Latgalians) — all Eastern Balts — as well as the Old Prussians, Yotvingians and Galindians — the Western Balts — whose languages and cultures are now extinct.
Medieval German chronicler Adam of Bremen in the latter part of the 11th century AD was the first writer to use the term "Baltic" in reference to the sea of that name. Before him various ancient places names, such as Balcia, were used in reference to a supposed island in the Baltic Sea.
Adam, a speaker of German, connected Balt- with belt, a word with which he was familiar.
In Germanic languages there was some form of the toponym East Sea until after about the year 1600, when maps in English began to label it as the Baltic Sea. By 1840, German nobles of the Governorate of Livonia adopted the term "Balts" to distinguish themselves from Germans of Germany. They spoke an exclusive dialect, Baltic German, which was regarded by many as the language of the Balts until 1919.
In 1845, Georg Heinrich Ferdinand Nesselmann proposed a distinct language group for Latvian, Lithuanian, and Old Prussian, which he termed Baltic. The term became prevalent after Latvia and Lithuania gained independence in 1918. Up until the early 20th century, either "Latvian" or "Lithuanian" could be used to mean the entire language family.
The Balts or Baltic peoples, defined as speakers of one of the Baltic languages, a branch of the Indo-European language family, are descended from a group of Indo-European tribes who settled the area between the lower Vistula and southeast shore of the Baltic Sea and upper Daugava and Dnieper rivers. Because the thousands of lakes and swamps in this area contributed to the Balts' geographical isolation, the Baltic languages retain a number of conservative or archaic features.