An Etymological Dictionary of the German Language/Trauer
Trauer, f., ‘mourning, sorrow, grief,’ from the equiv. MidHG. trûre, f.; a derivative of MidHG. trûren, OHG. trûrên (equiv. to ModHG. trauern, ‘to mourn, grieve’), wk. vb. Allied to ModHG. traurig, ‘mournful, sad,’ MidHG. trûrec, OHG. *trûrac (g); to this adj. AS. dreórig, E. dreary, is related by gradation (comp. Du. treurtg, ‘sad.’ Borrowed from HG.?). On account of OHG. trûrên, ‘to lower one's eyes,’ the cognates are based on the OTeut. root drus, ‘to fall, sink’ (comp. Goth. driusan, AS. dreósan, ‘to fall’).