The differentiation between Lithuanian and Latvian started after 800, with a long period of being one language but different dialects.
At a minimum, transitional dialects existed until the 14th century or 15th century, and perhaps as late as the 17th century.
Participants in this movement laid the foundations for standard Latvian and also popularized the Latvianization of loan words.
However, in the 1880s, when Czar Alexander III came into power, Russification started.
After the czar's death, around the start of the 20th century, nationalist movements reemerged.
For example, a place such as Lecropt (a Scottish parish) is likely to become Lekropta; the Scottish village of Tillicoultry becomes Tilikutrija.
This is a good example of linguistic purism in this language.
During the Soviet occupation (1940–1991), the policy of Russification greatly affected the Latvian language.
Throughout this period, many Latvians and Latvia’s other ethnicities faced deportation and persecution.