An Etymological Dictionary of the German Language/Annotated/foltern
foltern, verb, ‘to put to the rack, torture,’ from late Middle High German vultern, ‘to put on the rack.’ Akin to Folter, ‘rack,’ early ModHG only. of obscure origin. It is most frequently considered to be partly translated and partly borrowed from Middle Latin pulletrus, poledrus, properly ‘colt,’ which signifies ‘rack’ in Spanish and Portuguese (potro), “like Latin equuleus from equus, because it bore some resemblance to a horse.” Middle Latin poledrum is derived again from Greek πῶλος, ‘foal.’ “The wooden horse and the wooden ass — frames with a sharp-edged back, upon which the delinquents were compelled to ride — were favourite instruments of torture.”