you could have knocked me, etc. down with a feather

you could have knocked me down with a feather

An expression of great or utter surprise, bewilderment, or astonishment. I was so taken aback when I found out I'd won the lottery that you could have knocked me down with a feather!
See also: could, down, feather, have, knock
Farlex Dictionary of Idioms.

you could have knocked me, etc. down with a ˈfeather

(informal) used to tell somebody about a very surprising experience: When they said how much the painting was worth, you could have knocked me down with a feather!
See also: could, down, feather, have, knock
Farlex Partner Idioms Dictionary
See also:
  • you could have knocked me down with a feather
  • take aback, to
  • I'll be damned
  • knock (one) on the floor
  • knock (one) on the ground
  • I'll be hanged
  • I'll be!
  • (well,) I'll be hanged!
  • (well,) I'll be!