Just curious as to where this expression came from and when it came into being. It's one that is commonly used (among other variations, e.g. "Oh for crying out loud!"), but where does it come from originally?
For Pete's sake is attested from 1924, probably a euphemistic use of the disciple's name in place of Christ;
For Pete's sake can be found earlier than 1924.
1903's The Pedagogical Seminary and Journal of Genetic Psychology, Vol. X., includes a paper called "Children's Interests in Words, Slang, Stories, Etc." by Edward Conradi.
From page 377 in a list of slang expressions used by girls: