Either I’m having a massive brain fart or there is an Illuminati plot against me from ever learning what in the heck the origin of the word ( brace yourselves) P.U. is.
Yeah, you read that right: PU as in stinkum.
I have looked in about fifteen dictionaries (english, german, french) over the past few months and can’t find one trace of what these two little letters mean. How did PU come to mean " who cut the cheese?" 
Have I lost my mind or what?
I am only specualting, but perhaps it is a slang abbreviation for “pungent.”
Nah, pungent can’t be it.
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From [“http://www.geocities.com/~tenaswawa/gibbsi.htm”]Dictionary of Chinook Jargon
"Piu-piu, n. French, PUER, to stink. Or from the sound often uttered expressive of disgust at a bad smell. A skunk. "
Also puteo is Latin for “to stink, be redollent, smell bad”
From Latin Dictionary
IMO, “P.U.” comes from “pyew”, which probably comes from the French “piu-piu”.
“Pyew” can be intensified by saying “PeeeeYEEEW!”, which can sound like “P.U.”
Wow. You dopers are great. I had a feeling it was a french word some how, but dang it, I could not find it.
My mind is now at rest.( Like my metabolism)
I thank you.
Hey, there’s a book called Who Cut the Cheese by Jim Dawson. The link to Amazon actually has the author’s email addy… I bet he can answer the question!!
It’s also the initials of Pharmacia Upjohn, PU.
With Monsanto added, they can be MUP or PUM