An Etymological Dictionary of the German Language/dunkel

by Friedrich Kluge

dunkel, adj., ‘dark, gloomy, obscure,’ with MidG. initial d; from MidHG. tunkel, ‘dark, dull, damp,’ OHG. tunchal (with the parallel form tunchar, MidLG. dunker). By another stage of gradation OIc. døkkr, OFris. djunk are formed from the same root; they presuppose a Goth. *diggs (pre-Teut. dhengwos). The primit. allied E. dank points to a connection with dumpf (Teut. root dinq, dump).