The change from patronymics to set surname came about in the late 1880s to 1890s. The natural Finnish way of referring to someone's parentage is the genitive: ''Matin Olli'' ("Matthew's Olaf") instead of the solemn ''Olli Matinpoika'' ("Olaf Matthew's son")<ref>https://en.wikipedia.org/wiki/Finnish_name#Patronymics</ref>