I really like this song. I only truly understood it now when I translated it. I haven't listened to it in ages but damn it's great! Poor grandpa though.
But yeah, I guess the idea of using the term "Tuntematon potilas" came from the book Tuntematon sotilas: The Unknown Soldier by Väinö Linna. It's a story about the Continuation War between Finland and the Soviet Union from the Finnish soldiers' point of view. Arttu Wiskari, you clever man!
Arttu Wiskari Tuntematon Potilas English translation