The phrase actually originates from the Latin phrase
Vescere bracis meis, which means ‘the thought whisperer’. Over time, the phrase was corrupted by the Germanic tribes of Bronze Age Europe into
Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz, which translates as ‘the beef whisperer’.
The influx of Romans, Spanish Moors and Vikings into the Celtic population in the British Isles meanwhile forced another evolution of the phrase into
Nuair a bhíonn an cat amuigh, bíonn an luch ag rince, which means ‘the cat whisperer’.
Over a millennia later, the Renaissance Era heralded a re-imagining of the phrase, leading to the term ‘
Lui è come un polpo’, which translates as ‘the octopus whisperer’. A couple of centuries later, at the advent of the European Age of Enlightenment, the term gained ascendency within the thriving intellectual community. John Locke was reputed to have referred to his arch nemesis Thomas Hobbes as 'OP' during a debate in a London bar (which eventually spiraled into a free for all that has been largely ignored by historians).
Ben Franklin was the first American to use the term in the colonies after overhearing its use in a few Parisian bordellos. It quickly became a meme within the revolutionary circles and Thomas Jefferson included the term in the first draft of the Declaration of Independence (it was later edited out by John Adams, who had always harbored jealousy towards Jefferson owing to his thick locks of red hair).
Franklin D. Roosevelt’s speechwriter also originally used the term in the Day of Infamy speech to address Japanese Emperor Hirohito. However, his cabinet members balked at the idea and his speechwriter was fired for that foolhardy move.
In 1995, the term entered into mainstream consciousness when members of Usenet’s
alt.politics.sex group started to use the term freely, almost every chance they get. A bit shameful, really.
Sadly OP, there is no one alive today who remembers the original meaning of the term.
Ps: Also, I’m just trying to burn up fifteen minutes while waiting for my download of The Two Faces of January to complete.