Olsen would be from Norway, yes. The en name ending is from Norway and Denmark. In Sweden it is spelled Olson or Olsson. Anderson is spelled Andersen in Norway and Denmark, while in Sweden it’s spelled Andersson with two s. In Swedish, there is no apostrophes. So in English we would say: “Anders’ or John’s son, while in Swedish we would just add an s : “Johns son”. Hence the two s. The same is true for Johnasson. The “J” in Swedish is pronounced with a “y” sound. The last name “Skog”: skog is a Swedish word for “forest”.