Green’s Dictionary of Slang

(US campus) an expresssion of annoyance or dismissal.

1947		(con. 1942) J.H. Burns Gallery (1948) 175: ‘But they’re commissioned officers in the United States Army.’ ‘Ah, crud. They’ll do as they’re tole.’.
1995		Eble Campus Sl. Dec. 2: crud – expression of dismay, vexation. ‘Oh, crud, my shoe is stuck in the door.’.