Humans are believed to be the only ones to have the gift of language. Although Bible claims to explain the origin of languages and proclaims it as a punishment, most of the people are proud of their language and wish to make it more popular. Thus, not always it is legitimate.
As a country, Latvia appeared only in the early 20th century, precisely, on the 18th of November 1918. A year earlier Latgale made the decision to join it. Although it is considered as a part of Latvia, it had a very different history. Together with Kurzeme (together with Zemgale) and Vidzeme it duly belonged to Holy Roman Empire, Poland- Lithuania, Russia. While ruled by Russian empire- there was a very important difference- Kurzeme and Vidzeme together with Estonia was the Baltic province while Latgale was a part of another Russian province and with this did not have the priorities the Baltic province had.
For example- bondage was abolished in 1817 in Kurzeme, in 1819 in Vidzeme and only in 1861 together with the whole Russian empire in Latgale. As seen- Kurzeme and Vidzeme was economically more developed and Riga was the 3rd biggest industrial city in Russian Empire. Latgale had its misfortune in 1863 again as the Latin alphabet was forbidden. With this the use of Y could be explained because Cyrillic has such letter. Probably the next main difference is religion. While the main confessions in Latvia are Roman Catholic and Lutheran, in Latgale it is Orthodoxy.
Speaking historically its background is very different. Not only that- in Latgale Latvians are the minority and perceptually there is the biggest number of foreigners. So it is no great wonder that Latgalian is different from Latvian. Yet- as known- the first resident of Latvia arrived 9,000 BC, Finno-Ugric tribes arrived...