crud (n.)
"nonsense, rubbish," 1940, U.S. slang; originally 1920s army and college student slang for "venereal disease." Said to be a metathesis variant of curd, which actually makes it an unconscious return to the original Middle English form of that word (see curd). As G.I. name for "disease of any and every sort" it is attested from 1945.