Pish posh is an expression for giving voice to doubts, disdain and contempt.
It is mostly used for calling a story absurdly unbelievable.
The term “pish” was used as a word for contempt as far back as the 1500’s in Britain.
It appeared in William Shakespeare’s Henry V play as well.
The “posh” part of the expression was added to the phrase sometime during the 1800’s or the early 1900’s.
“Pish posh” is still in use today and it is a much more refined way of calling bs on something, than actually saying “bullshit”.
It was defined on Urban Dictionary in 2003.