Archduke ( Erzherzog ) is a title distinct from Grand Duke ( GroÃ herzog or GroÃ fÃ 1\/4 rst ) that is used in some other German royal houses and still in sovereign Luxemburg . Archduke ( in German Erzherzog ) is a title distinct from Grand Duke ( in German GroÃ herzog ) , used in some other German royal houses and still in sovereign Luxembourg .