What ethnicity is the last name Sak?

Polish: from a reduced form of the personal name Isaak (see Isaac). Polish and Hungarian (Szák): from Polish sak, Hungarian szák, 'fishing net', 'sack', hence a metonymic occupational name for a maker of nets or sacks. Dutch: variant of Zack, a short form of the personal name Zacharias or Isaak. Jewish (Ashkenazic): variant spelling of Sack.