rhubarb

The word traces to Late Latin reubarbarum, likely from Greek ῥῆον βαρβαρικόν, meaning "foreign rhubarb root" — combining the plant's own name with barbarikón, "foreign or barbaric." The Greek term for the plant itself may echo Ῥᾶ, the ancient name for the Volga River, near where the plant originated, though its deepest root traces to a Proto-Iranian word for rhubarb or fennel.

Beyond its botanical sense, the word took on a second life in the theatre: around 1852, actors at Charles Kean's Princess's Theatre would murmur it repeatedly to fake the sound of indistinct crowd chatter. This trick later crossed to American radio dramas, and from there baseball commentator Red Barber applied it to on-field arguments too garbled to make out — turning a stage trick into slang for any noisy dispute.

The word has cognates across Europe — Italian rabarbaro, German Rhabarber, Spanish ruibarbo, and Dutch rabarber among them — all descending from the same Latin and Greek roots.