An Etymological Dictionary of the German Language/Rohr
Rohr, n., ‘reed, cane, rush,’ from the equiv. MidHG. and OHG. rôr (gen. rôres), n.; an earlier *rauza is to be assumed; comp. Goth. raus, n., OIc. reyr, m., Du. roer, ‘reed’ (wanting in OSax., AS., and E.). The Teut. form in s, closely allied to the Goth., passed into Rom.; comp. Fr. roseau, ‘creed’ and the equiv. Prov. raus. The form rausa-, with which Reuse and Röhre (Rost, (1)?) are also connected, is related to Lat. ruscum, ‘butcher's broom’; comp. Moos with Lat. muscus.