An Etymological Dictionary of the German Language/taugen
taugen, vb., ‘to be of use, be good or fit for,’ from MidHG. tugen, OHG. tugan (pres. sing. touc), pret. pres., ‘to be capable, useful, suitable, to be of use, to suit.’ Corresponding to OSax. dugan, ‘to be capable, be of use,’ Du. deugen, ‘to be of use,’ AS. dugan, OIc. duga, Goth. dugan, ‘to be fit, of use’ The Teut. verbal root dug (daug) might, like Lith. daúg, ‘much,’ daúksinti, ‘to increase,’ point to Aryan dhugh (Gr. τύχη, ‘fortune,’ τυγχάνω, ‘I am fortunate’?). To this are allied tüchtig and Tugend.