Green’s Dictionary of Slang

abbr. of I’ll be damned!

1929		J.B. Priestley Good Companions 377: ‘Well, I’ll be –’ Joe did not say what he would be, but simply blew out his breath.
1970		A. Young Snakes (1971) 74: I’ll be! You mean that band you all got? Well, I’ll just be!
1972		(con. 1916) G. Swarthout Tin Lizzie Troop (1978) 185: ‘Well, I’ll be,’ said Carberry.
2000		C. Cook Robbers (2001) 13: That brake fluid done stained my pants. The Ranger took a look. I’ll be, it sure nuff did.