um-um-um

“And all was still but the _um-um-um_ of the great beetle or chafer which had passed in through the window, and began circling round just below the whitewashed ceiling, against which its wings brushed from time to time with a faint fizz, till all at once Rodd started up, for his uncle exclaimed --”

The Ocean Cat's Paw The Story of a Strange Cruise

“Mr.. Gibson came upon Mr. Henderson's name once, and then went on with a running um-um-um to herself, which sounded very mysterious, but which might as well have been omitted, as all that Cynthia really said about him was, 'Mr. Henderson's mother has advised my aunt to consult a certain Dr”

Wives and Daughters