In Norway, unless they were tradesmen in town or aristocratic, they did not have last names or middle names. So if you see Olsen with a name following, that extra name is a farm name where he lived. The name 'Jens Olsen Farm' would mean Jens was his name, his only name, and he was the son of Ole, and he lived at Farm. We now assign last names from those for our own convenience, to fit our current naming systems. You have to search all the combinations!
They also did not spell names, didn't usually read or write. Names as recorded were put down by others, such as clerics, and spelled whatever way that person thought it should be. Then arbitrarily changed by an immigration agent! And then sometimes changed by themselves to fit in with Americans.