On the QT
Q From Mike Willis: I’m trying to find out the origin of the phrase, on the QT, meaning off the record or in confidence.
A We’re not at all sure of the origin, though it's clear it's from the US, yet another example of that love for abbreviations that was a linguistic feature of nineteenth-century America and which has given us those other famous examples OK and PDQ.
According to Robert Hendrickson, in The Facts on File Encyclopedia of Word and Phrase Origins, the first reference is from a British ballad of 1870, which contained the line “Whatever I tell you is on the QT”. Unfortunately, he doesn’t give the title of the ballad and, so far as I know, nobody has been able to track it down.
The Oxford English Dictionary has a first sighting from 1884, which appeared in Mummer's Wife by George Moore: “It will be possible to have one spree on the strict q.t.”. It’s possible to take that back a little way, to what looks like a vaudeville song of 1879 that was published in the Cambridge Jeffersonian of Ohio:
My house-keeper, Mrs. Brown,
Is the greatest saint in town,
As tee-total as it’s possible to be,
It’s only by her nose
I know where my whiskey goes,
She tipples on the strict Q. T.
It seems to have been just an abbreviated spelling, using the first and last letters of the word quiet, the mild obfuscation also suggesting a meaning for the expression.