Latgalian language
Originally Latgalians were a tribe living in modern Vidzeme and Latgale. It is thought that they spoke the Latvian language, which later spread through the rest of modern Latvia, absorbing features of the Old Curonian, Semigallian, Selonian and Livonian languages. The Latgale area became politically separated during the Polish–Swedish wars, remaining part of the Polish–Lithuanian Commonwealth as the Inflanty Voivodeship, while the rest of Latvians lived in lands dominated by Baltic German nobility. Both centuries of separate development and the influence of different prestige languages likely contributed to the development of modern Latgalian as distinct from the language spoken in Vidzeme and other parts of Latvia.
Balts
The Balts or Baltic people (, ) are an Indo-European ethno-linguistic group who speak the Baltic languages, a branch of the Indo-European language family, which was originally spoken by tribes living in the area east of Jutland peninsula in the west and in the Moscow, Oka and Volga rivers basins in the east. One of the features of Baltic languages is the number of conservative or archaic features retained. Among the Baltic peoples are modern Lithuanians, 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.