rhubarber
/ˈruːbɑːbə/noun
1A person who grows rhubarb.
2 Slang (originally Theatre ). Originally: an actor who repeats the word ‘rhubarb’ so as to represent an indistinct conversation or the noise of a crowd. Now also (more generally): a person who mumbles or speaks indistinctly.
Origin
Early 20th century; earliest use found in Munsey's Magazine. From rhubarb + -er.