You will notice that some/many surnames claim its origin from many nationalities. There are two main reasons for that. Firstly, some occupations existed in not just one country. Like a very popular surname 'Smith' is derived from the occupation that had to exist pretty much in every village, which made the name very popular in the Western countries. Secondly, people just keep moving around the globe. They move and they stay. Eventually the new surnames become parts of the new culture.