Green’s Dictionary of Slang

(US) as a euph. for the past participle of damn v. (2); usu. in the phr. I’ll be jim-whizzed!

1890

World (N.Y.) 8 July 3/1: To his surprise Dave was standing ten feet away from the bag paralyzed with astonishment. ‘Well, I’ll be jim-whizzed,’ was all that Dave said.