What does p.u. mean?

Everyone says it when odorifious scents fill the air. Mention those 2 letters in a crowd and everyone’s nostrils do their little dance. But what does p.u. mean? Even Acronym Finder states it is not an acronym. It had to come from somewhere. Any ideas?

It’s “short” for phewwwwww!!!

This web page traces it back to Sanskrit:

http://hinduwebsite.com/general/sanskrit_english.htm

This one makes note of the PIE root *pu, meaning “rot, stink”
http://www.etymonline.com/p11etym.htm

This appears to be a very ancient word.

Try the Phrase Finder.