Names like Schmedes:Can you tell me how?

This my sound silly but Nowadays you may find a name like Tymika or Joshua or Angela in any ethnic group,Still I've always wonder how last names are so dramatically changed...Like the name Schmedes for a brown skinned person or hispanic,Jiminez is hispanic,Arusu is African What is Schmedes and Blanding and how did unusual names like these enter other ethnic groups.....I mean was it ped down through generations or through recent decades in marriage?