An Etymological Dictionary of the German Language/Zaun
Zaun, m., ‘hedge, fence,’ from the equiv. MidHG. zûn, m.; comp. OSax. tûn, Du. tuin, ‘hedge, garden,’ AS. tûn, ‘enclosure, place,’ E. town (also dial. to tine, ‘to hedge in,’ from the equiv. AS. tŷnan), OIc. tún, ‘enclosure, farm.’ Teut. tû-no- (tû-nu-?) is connected pre-historically with -dûman in OKelt. names of places (such as Augustodûnum, Lugdûnum); comp. OIr. dún, ‘citadel, town.’ —