Latvian language
Latvian ("Latviešu valoda" ) is a Baltic language spoken in the Baltic region. It is the language of Latvians and the official language of Latvia as well as one of the official languages of the European Union. It is sometimes known in English as Lettish, and cognates of the word remain the most commonly used name for the Latvian language in Germanic languages other than English. There are about 1.3 million native Latvian speakers in Latvia and 100,000 abroad. Altogether, 2 million, or 80% of the population of Latvia, speak Latvian. Of those, 1.16 million or 56% use it as their primary language at home. The use of the Latvian language in various areas of social life in Latvia is increasing.
Latgalians
They likely spoke the Latvian language, which probably became the "lingua franca" in present-day Latvia during the Northern Crusades due to their alliance with the crusaders. Latgalians later assimilated the neighbouring tribes, forming the core of modern Latvians.