An Etymological Dictionary of the German Language/Annotated/Zaun
Zaun, masculine, ‘hedge, fence,’ from the equivalent Middle High German zûn, masculine; compare Old Saxon tûn, Dutch tuin, ‘hedge, garden,’ Anglo-Saxon tûn, ‘enclosure, place,’ English town (also dialectic to tine, ‘to hedge in,’ from the equivalent Anglo-Saxon tŷnan), Old Icelandic tún, ‘enclosure, farm.’ Teutonic tû-no- (tû-nu-?) is connected pre-historically with -dûman in Old Keltic names of places (such as Augustodûnum, Lugdûnum); compare Old Irish dún, ‘citadel, town.’ —