Surnames, in ancient times where a way of identifying who is in your family, such as if your father's name was John, and you were steve, then your surname might be Johnson, as you are John's son. The swedes did this so it is very hard to track family tree because of it. My ex was Olafson, meaning son of Olaf, or some surnames where based on where you were born so the town village etc. Would have been incorportated in your name ie. Jesus of Bethlehem
