knock someone over with a feather

Verb

knock someone over with a feather (third-person singular simple present knocks someone over with a feather, present participle knocking someone over with a feather, simple past and past participle knocked someone over with a feather)

1. (excessive, idiomatic, informal) To greatly surprise or astonish someone.
   • She hardly, she said, believed her own senses. You might have knocked her down with a feather. She did not know whether she stood on her head or her heels.1838 February 17, “Review of Books. Hood’s Own. No. 1. Baily.”, in The Idler, and Breakfast-table Companion; a New and Fashionable Weekly Journal of Literature, Fine Arts, Music, Amusement...
   • "I thought you might see what she's up to if she is up to something, and I'm pretty sure she is." / "You could knock me over with a feather," Jane said. "Well! Yes, it does sound as though she's up to something I'd be inclined to say. But you can't be sure with an odd one like Sue. Might be a touch...1977, Joe Ashby Porter, chapter 50, in Eelgrass (A New Directions Book [New Directions Paperbook]; [438]), New York, N.Y.: New Directions Publishing, →ISBN, pages 102–103