An Etymological Dictionary of the German Language/Annotated/Rohr
Rohr, neuter, ‘reed, cane, rush,’ from the equivalent Middle High German and Old High German rôr (genitive rôres), neuter; an earlier *rauza is to be assumed; compare Gothic raus, neuter, Old Icelandic reyr, masculine, Dutch roer, ‘reed’ (wanting in Old Saxon, Anglo-Saxon, and English). The Teutonic form in s, closely allied to the Gothic, passed into Romance; compare French roseau, ‘creed’ and the equivalent Provençal raus. The form rausa-, with which Reuse and Röhre (Rost, (1)?) are also connected, is related to Latin ruscum, ‘butcher's broom’; compare Moos with Latin muscus.