But Hagrid simply waved his hand and said, “About our world, I mean. Your world. My world. Yer parents’ world.” “What world?” Hagrid looked as if he was about to explode. “DURSLEY!” he boomed. Uncle Vernon, who had gone very pale, whispered something that sounded like “Mimblewimble.” “But yeh must know about yer mom and dad,” he said. “I mean, they're famous. You're famous.”
It's from Harry Potter and the Philosopher's Stone, chapter 4, The Keeper of the Keys.
Does he curse Hagrid to lose sound? Does the word "Mimblewimble" sound like anything meaningful with it, so that he would choose to say it? It can't be a coincidence. I'd like to know what's the idea that comes to mind when hearing 'Mimblewimble'.