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
In the 1925 census Russians were already reported as the largest minority (10.6%) and Russian was spoken as the family language by 14% of inhabitants. A small percent of Russian speakers were not ethnic Russians and conversely a small percentage of ethnic Russians used another language in family, which was attributed to mixed marriages, living in area with another majority language and, in case of Russian speakers, Russification policies of Russian empire. In 1930 census Russian was reported as family language by 13% of inhabitants.