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.
Russian language in Latvia
A 2012 research "Language situation in Latvia: 2004–2010" by the Latvian Language Agency reported that the overall proficiency of Russian as a second language is decreasing due to it losing its popularity among the youth, especially in areas with a very large Latvian majority. In a 2004 survey 73% of the Latvian respondents rated their Russian language skills as good, but in 2008 the overall proportion had decreased to 69%.