Finnskog is a name for the area in Central Sweden and Norway, which was in the 17th century settled by the Finns from Savo region and northern Häme (at that time, Finland was a part of Sweden). They stayed here and they presence is still to be seen not only in the landscape (they practised the slash and burn type of farmin) but most of all in place-names.
The presentation is based on my own experience with the area (hiking the 250km long Finnskogleden /trail/ but on the research of Finnish, Swedish and Norwegen linguists and folklorists (e.g. Julius Mägiste and Tuula Eskeland).