Andresen is it a Jewish name?

Answer 1

Andresen is a Scandinavian name literally meaning "the son of Anders/Andreas/Andrew" or some other variant of the name Andrew.

However, somebody with the name could still be Jewish. Because Judaism passes from the mother to a new generation but children usually take their father's surname, if a Jewish woman marries a gentile (non-Jewish) man, her children will - according to halakha (Jewish law) be Jewish but will not have a Jewish surname. An example of this would be the English actor and comedian Stephen Fry who has a Jewish mother and therefore is Jewish himself, despite his non-Jewish surname.