Assuming that the family name is a place name perhaps with the
     common suffix -er (as in Oberheimer), then it is very possible that
     the family did indeed come from that place (Oberheim) originally.

     But they probably left that place before they acquired the surname,
     which was probably before the earliest extant records, so you will
     likely never be able to prove it.  Also note that place names are
     often shared by several towns, and that a surname may be related
     etymologically but not genealogically to a place name.