One of the many memorable pieces of wordplay in The Phantom Tollbooth is when the heroes meet Dr Dischord and his assistant, the awful DYNNE.
"You mean you've never met the awful DYNNE before?" said Dr. Dischord in a surprised tone. "Why, I thought everyone had. When you're playing in your room and making a great amount of noise, what do they tell you to stop?"
"That awful din," admitted Milo.
"When the neighbors are playing their radio too loud, late at night, what do you wish they'd turn down?"
"The awful din," answered Tock.
"When the street on your block is being repaired and the pneumatic drills are working all day, what does everyone complain of?"
"The dreadful row," volunteered the Humbug brightly.
"The dreadful RAUW," cried the anguished DYNNE, "was my grandfather. He perished in the great silence epidemic of 1712."
What, if anything, does "the great silence epidemic of 1712" refer to? Did something significant happen in that year which led to a reduction of noise in the world? (Trying to recall this line from memory, I misremembered it as 1918, which would have made sense as the end of a world war would surely have reduced noise levels.)