From Middle English rubarbe or Anglo-Norman reubarbe, from Middle French reubarbe, rubarbe, rebarbe, reu barbare (“rhubarb”) (modern French rhubarbe), from Late Latin reubarbarum, rheubarbarum, rubarbera, rybarba, probably from Koine Greek ῥῆον βάρβαρον (rhêon bárbaron) (ῥῆον (rhêon, “rhubarb”) + Ancient Greek βάρβαρον (bárbaron), neuter of βάρβαρος (bárbaros, “foreign; barbaric”)). It has also been suggested the Latin terms are from Latin Rha (“the River Volga”) (which is in the region from which the plant came to the Mediterranean, cognate with New Latin Rheum) + barbarum (“barbarian”).
The word is cognate with Catalan riubarb, riubarbar, riubàrbara, riubarber, riubarbre, etc. (now Catalan ruibarbre); Italian rabarbero, reubarbaro, ribarbaro, ribarbero, riobarbaro, etc. (now rabarbaro); Middle Dutch rebarbe, rebarber; Dutch rhabarber, rhabarbo, robarber, rubarbe, rubarber, etc. (now rabarber); Middle High German rebarbe, reubarber (early modern German rabarber, reubarbar, rhabarbara; German Rhabarber); Middle Low German rebarbar, rebarber, reubarbar, reubarber; Old Provençal reubarbe; Portuguese reubarbo, rheubarbo (now ruibarbo); Spanish ruibarbvo (now ruibarbo).
- Any plant of the genus Rheum, especially Rheum rharbarbarum, having large leaves and long green or reddish acidic leafstalks, that are edible, in particular when cooked (although the leaves are mildly poisonous).
- The dried rhizome and roots of Rheum palmatum or Rheum officinale, from China, used as a laxative and purgative.
- (military) An RAF World War II code name for operations by aircraft (fighters and fighter bombers) seeking opportunity targets.
Attributed to the circa 1852 practice by the theatre company of English actor Charles Kean (1811–1868) at the Princess's Theatre, London, of actors saying the word rhubarb repetitively to mimic the sound of indistinct conversation, the word having been chosen because it does not have harsh-sounding consonants or clear vowels.
The baseball senses are said to have been coined by the American sports writer Garry Schumacher and popularized by the American baseball commentator Red Barber (1908–1992). Barber also claimed to have started using the word in the 1940s, based on the practice in “early radio dramas” (presumably in the US, circa 1930) of actors repetitively voicing rhubarb. However, unlike the UK usage, he felt the practice applied to muttering by an angry mob, and so applied the word to arguments on the baseball field where he could not distinguish the words.
- (uncountable) General background noise caused by several simultaneous conversations, none of which is decipherable; specifically such noise created in films, stage plays, etc., by actors repeating the word rhubarb; rhubarb rhubarb, rhubarb rhubarb rhubarb.
- (US, originally _ baseball, countable) An excited, angry exchange of words, especially at a sporting event.
- (US, originally _ baseball, by extension, countable) A brawl.