Andersen (Danish pronunciation: [ˈɑnɐsn̩]) is a Danish-Norwegian patronymic surname meaning "son of Anders" (itself derived from the Greek name "Ανδρέας/Andreas", cf. English Andrew). It is the fifth most common surname in Denmark, shared by about 3.2% of the population. From the same root – the given name Andreas – derives the surname Andreasen Danish pronunciation: [ænˈtʁeˀæsn̩] (cognate Andreassen) and Andresen Danish pronunciation: [ænˈtʁeˀsn̩]. The numbers of bearers of the surnames Andersen, Andreasen, Andreassen and Andresen in Denmark and Norway (2009): Persons.
https://en.wikipedia.org/wiki/Andersen