An Etymological Dictionary of the German Language/Annotated/Tülle
Tülle, feminine, ‘socket,’ Middle High German tülle, neuter, ‘ferule for fastening an iron point on a handle’ (usually ‘partition of boards, palisade’). Old High German has no corresponding form *tulli (Gothic *dulja-), which might be connected by gradation with Modern High German Thal (Tülle, literally ‘deepening’). Others consider French douille (from Latin ductile, ‘channel’), ‘socket,’ as the ultimate source of Middle High German tülle. French tuyau (English tewel), Spanish tudel, ‘pipe,’ are certainly not allied. The abnormal double sense of Middle High German tülle has not, however, been explained.