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.
Baltic states
The Estonian language is a Finnic language, together with neighboring Finland′s Finnish language.
Apart from the indigenous languages, German was the dominant language in Estonia and Latvia in academics, professional life, and upper society from the 13th century until World War I. Polish served a similar function in Lithuania. Numerous Swedish loanwords have made it into the Estonian language; it was under the Swedish rule that schools were established and education propagated in the 17th century. Swedish remains spoken in Estonia, particularly the Estonian Swedish dialect of the Estonian Swedes of northern Estonia and the islands (though many fled to Sweden as the Soviet Union invaded and re-occupied Estonia in 1944). There is also significant proficiency in Finnish in Estonia owing to its closeness to the native Estonian and also the widespread practice of listening to Finnish broadcasts during the Soviet era. Russian also achieved significant usage particularly in commerce.