Who's Pete?

When people say “For Pete’s sake” who is Pete? And how did this quote become attributed to him?

Please sight reference.
Thank you for your time.

I thought Cecil would have covered this, but but my search didn’t find a column.
Most of what I turned up says it refers to St. Peter, Delila.
Here’s one site that covers it:
http://groups.yahoo.com/group/Ask-The-Rick/message/7

There was a thread on this a while ago, but I’m not going to try searching for it until the boards speed up a bit. Pete is St. Peter, gatekeeper of Heaven. It’s a euphemism for “for God’s sake”, but you replace God with some other heavenly VIP, typically Pete or Mike (St. Michael the Archangel).

Pete/Mike