An Etymological Dictionary of the German Language/Düne
Düne, f., ‘down, dune,’ simply ModHG. from the equiv. LG. düne (OSax. *dûna), Du. duin (whence Fr. dune); respecting ModHG. ü from Du. ui, comp. Büse, Süden. Akin to AS. dûn, ‘hill,’ E. down (‘plateau’), So too E. down, adv.; for AS. adûne, ofdûne, ‘from the mountain, towards the valley,’ corresponds exactly to MidHG. ze tal (comp. Fr. à mont, ‘up the stream’). Likewise Gr. θύραζε, ‘before the door,’ has the general meaning ‘outside’; MidHG. ze bërge is ‘aloft, upwards’; comp. ModHG. die, Haare stehen einem zu Berge, ‘one's hair stands on end.’ The düne group (E. down) seems to have spread from Eng. into Du. and LG. (comp. besides Bake, Boot, Prahm). Hence the assumption that AS. dûn is of Kelt. origin is not to be discarded — OIr. dûn, ‘hill’ (comp. the OKelt. names of towns ending in dûnum, Augustodiunum, Lugdunum); though the attempt to show that it is primit. allied to Gr. θῖν (nom. θίς), ‘sea-beach,’ and Sans. dhánu-s, ‘dry land, continent, inhospitable land,’ cannot be recommended; AS. dûn would be pre-Teut. dhûnâ (the indubitable form of the cognate word in Ind.).