An Etymological Dictionary of the German Language/Annotated/Rhabarber
Rhabarber, masculine, ‘rhubarb,’ Modern High German only, from Italian rabarbaro, French rhubarbe; also earlier Modern High German Rhapontif, from French rapontique. The word is based on the Middle Latin ra-, reu-ponticum, -barbarum, also radix pontica, -barbara, ‘a plant growing on the banks of the Volga.’