First version

This phrase and phrases like “for Pete’s sake” are euphemisms for the phrases “for the love of God/Christ” or “for God’s/ Christ’s sake” and hail from a time when those phases were considered blasphemous. Nowadays phrases like “for the love of god” are commonly used, but the euphemisms are still used.

Why Pete? Most likely it is a reference to the catholic Saint Peter.

1st link below

http://members.aol.com/MorelandC/HaveOriginsData.htm

second version

FOR PETE’S SAKE – The phrase is simply a polite version of a common and profane expression involving the name of Christ. We’d surmise that the original ‘Pete’ was St. Peter.” From “Morris Dictionary of Word and Phrase Origins” by William and Mary Morris. Substituting less offensive words – like Godfrey Daniel for the other GD – is called a minced oath.

2nd link below

http://www.phrases.org.uk/bulletin_board/30/messages/1785.html

“Pete was originally St. Peter! What is the origin/menaing For Pete’s Sake? : From the archives: : Biblical origins. Think of St Peter. Think of the omnipresent medieval church and think of hitting your thumb with a hammer. You can’t swear, else the local priests will have you up before the Bishop and the Lord alone knows what the outcome of that will be, so you exclaim, in appropriate tone of voice, “For Saint Peter’s sake” and carry on erecting the shelves. This phrase was amended to “For Pete’s Sake” in later, less religiously oppressive, times. : This is called a “Minced oath,” a substitution of a less offensive word. FOR PETE’S SAKE – The phrase is simply a polite version of a common and profane expression involving the name of Christ. We’d surmise that the original ‘Pete’ was St. Peter.” From “Morris Dictionary of Word and Phrase Origins” by William and Mary Morris. Substituting less offensive words – like Godfrey Daniel for the other GD – is called a minced oath.

The answers above fall between fantasy or science fiction. Honestly, folks, get a grip.

People say that phrase because they don’t want to say “For God’s sake”, which would be blasphemy. Instead, they swear by St. Peter, who is apparently not as sensitive.

for petes sake originated from a line long for fanatic who lived in NJ

Actually the expression was originally:

For pee, T’s sake. (Sake being a japanese alcohol.)

T’s sake was a known diuretic. It would cause the flowing of an unusual amount of urine, or pee. And when those responsible for this slogan had drunk too much sake, they tended to slur their words. Hence the modern form of this expression, “for Pete’s sake”.

The ancient romans used to call GOD pete

LOL I love this question. I bet someone has answered while I am posting this.