blow the gaff

blow the gaff

slang To talk about or reveal a private or secret matter. Primarily heard in UK. I can't believe you blew the gaff and talked about the plans for her surprise party right to her face! Don't tell your little brother anything you want to keep secret because he'll definitely blow the gaff.
See also: blow, gaff

blow the gaff

BRITISH, INFORMAL
If you blow the gaff, you tell people something which was supposed to be kept secret. He is certainly not the first minister to blow the gaff. Note: `Blow' here means `reveal'. In the 19th century, `gaff' was a slang word used to refer to dishonest behaviour which was intended to deceive people.
See also: blow, gaff

blow the gaff

reveal or let out a plot or secret. British informal
The word gaff is recorded from the early 19th century, but its origins are uncertain.
See also: blow, gaff

blow the ˈgaff (on somebody/something)

(British English, informal) reveal a secret: She didn’t want anyone to know where she had been, but her husband blew the gaff. OPPOSITE: keep mum
See also: blow, gaff
References in classic literature ?
Now, sooner than let the Protectionists triumph, the Cobden Club itself would blow the gaff and point out to the workers that Protection only means compelling the proprietors of England to employ slaves resident in England and therefore presumably--though by no means necessarily--Englishmen.
A junior marine engineer on the liner Caribbean Princess, he risked his career to blow the gaff on illegal pollution by luxury cruise ships.
Across the town, the Cow and Snuffers where Disraeli is said to have dallied while on his way to meet a mistress - no kiss 'n' tell tabloids to blow the gaff.
And, without wishing to blow the gaff, I'm glad I did.
On the following pages we blow the gaff, no holds barred.
THE end of the road could be in sight for in-car radar detectors that blow the gaff on roadside speed cameras.
I have much experience of teaching adults and training adults out here in the real world so, with respect, your correspondent should take it easy and not blow the gaff for the teaching profession whose perks they all want to keep, thank you
In his final sentence Shapiro's literary piety threatens to blow the gaff on an otherwise worthy project in his platitudinous insistence that 'One things remains certain: as long as anxieties about racial, national, sexual, and religious difference continue to haunt the way we imagine ourselves and respond to others, Shakespeare's words will remain "not of an age, but for all time"' (229).
It will, I hope, blow the gaff on the treatment of the Queen Mother's relatives Nerissa and Katherine Bowes-Lyon, dumped into an institution in 1941 when aged 15 and 22 and, say ancient nurses who worked there, left to rot.
Your choice of sat-nav voice probably reveals more about your character than you think - or at least it does when your children blow the gaff.
And then along comes Ste' to blow the gaff,compounding it with probably one of the worst goalkeeping displays since Gary ``Careless Hands'' Sprake threw the ball in his own net in front of the Kop.