"Oh for Pete's Sake!"

I love finding out the etymology of words or how a famous quotation came into play. The Freakoconomics blog has been doing a feature where people email their queries about a specific quotation and Fred Shapiro tries to uncover how they came about. This one should have been obvious but somehow wasn't.

Beth Lavadia asked:

My mother used to say in exasperation to my sisters and I, “For Pete’s sake!” Who is this Pete fellow and why is his name used in such an expression?

This is usually thought to refer to St. Peter, chosen as a less offensive swear reference than Jesus or God. But in the etymology business, the proper answer is often “etymology unknown,” and no one knows for sure who this Pete fellow is.