Wikipedia
Finnicization (also finnicisation, fennicization, fennicisation) is the changing of one's personal names from other languages (usually Swedish) into Finnish. During the era of National Romanticism in Finland, many people, especially Fennomans, finnicized their previously Swedish family names.
Some of these people were descended from Finnish-speaking farmers, who had previously changed their Finnish names to Swedish ones after climbing society's ladder. This was an understandable stratagem, as official positions (and even many trades) were only open to those speaking Swedish, and a Finnish name would have been an impediment to success.
In the 18th century, Finnish recruits serving in the Swedish army were given short Swedish surnames such as Törn, Malm and Brun. This was because Swedish officers found Finnish names difficult to pronounce. Some of these names were later finnicized to Törni, Malmi, etc.
A notable event in finnicization was the centenary, in 1906, 100 years after the birth of the philosopher and statesman Johan Vilhelm Snellman. Author Johannes Linnankoski encouraged Finns to give up their Swedish names on 12 May, Snellman's birthday. During 1906 and 1907 about 70,000 Finns changed their names.