An Etymological Dictionary of the German Language/toll
toll, adj., ‘mad, frantic, absurd,’ from MidHG. and OHG. tol (with one l), adj., ‘foolish, absurd,’ to which OHG. tulisc, ‘foolish,’ is allied. Comp. OSax., Du., and AS. dol, ‘foolish,’ E. dull. The Teut. root dul contained in these words has a variant dwal, which has been preserved in Goth. dwals, foolish, AS. gedwëlan, ‘to err,’ OHG. gitwola, ‘infatuation, delusion, heresy,’ OSax. dwalm, ‘infatuation, delusion.’ An Aryan root dhwel, dhul, ‘to be infatuated, deluded,’ is also attested by Sans. dhvṛ, dhûr (dhru), ‘to deceive, cheat, injure.’