An Etymological Dictionary of the German Language/Annotated/Turm
Turm (Upper German and Rhenish Turn), masculine, ‘tower, steeple,’ from the equivalent Middle High German turm, with the variant turn (torm, torn), masculine; in Old High German only turra and turri, which correspond to the equivalent Latin turris. The final m of the Middle High German word has not yet been explained, nor the n of Old Dutch turn, Dutch toren, Upper German turn; Anglo-Saxon tûr, English tower, with the variant Anglo-Saxon torr, ‘tower,’ also present a difficulty. Compare further French tour, Italian torre, from Latin turris.