An Etymological Dictionary of the German Language/Turm
Turm (UpG. and Rhen. Turn), m., ‘tower, steeple,’ from the equiv. MidHG. turm, with the variant turn (torm, torn), m.; in OHG. only turra and turri, which correspond to the equiv. Lat. turris. The final m of the MidHG. word has not yet been explained, nor the n of ODu. turn, Du. toren, UpG. turn; AS. tûr, E. tower, with the variant AS. torr, ‘tower,’ also present a difficulty. Comp. further Fr. tour, Ital. torre, from Lat. turris.