What's the meaning of the phrase 'Private parts'?
Euphemism for the sexual organs.
What's the origin of the phrase 'Private parts'?
If ever there was an opportunity for a dramatic character called 'Private Parts' it must have been in the 16th outing of the innuendo laden 'Carry On' film series: Carry On Up The Khyber. In the event the film-makers must have considered that a step too far for a 1968 audience and opted instead for Charles Hawtrey's character 'Private Widdle'.
They need not have been so coy as 'privates' have been a part of British literature for centuries, beginning with no less a playwright as William Shakespeare. In Hamlet, 1604, the bard gives these lines to Hamlet and Guildenstern:
Then you live about her waist, or in the middle of her favours?
'Faith, her privates we.
As so often with Shakespeare Guildenstern's line has a double meaning. A Jacobean audience would he understood that 'privates' meant both genitals and 'people who hold no public office'.
That's a record of the word 'privates', and we don't have to wait very long for the expression 'private parts' to appear in print.
In 1623, Gervase Markham published a reference manual for the treatment of myriad maladies: Country Contentments: or, The Husbandmans Recreations. This contains an impressive list of cures for the medical problems that might beset a gentleman of the time, including 'pestilent fever', 'green sickness', 'fatness about the heart' and, interestingly for our purpose here, 'the diseases of the private parts'. Should you ever suffer from such, try this:
Take Agnustcastus [a.k.a. Chasteberry] and Castoreum [an ointment secreted by beavers] and seeth them together in wine and rinse thereof, also seeth them in vinegar and hot lappe it about the privy parts and it will helpe.
First catch your beaver (and no, I don't think that was a euphemism) and then wash your genitals in hot vinegar - hmm. Whether Markham's claim that the above remedy 'will helpe' stands up to scrutiny is open to doubt, but it sounds not unpleasant.
Since then 'private parts' has never been out of print and remains one of the better known euphemistic phrases.