Although Shakespeare refers to “hums and ha’s,” sifting through etiquette manuals and public-speaking guides turns up scant evidence of a prohibition against ums, ers and uhs, which are profuse in the first recording of Thomas Edison’s voice, in 1888. Mr. Erard, rather ingeniously, traces the prohibition on um and other speech flaws to the advent of radio in the early 1920s.
2007 August 24, William Grimes, “Uh, Lead My Rips: No More Bloopers”, in New York Times