The meaning and origin of the expression: Blow the gaff

Blow the gaff

What's the origin of the phrase 'Blow the gaff'?

When someone is said to blow the gaff it is usually when exposing some crime or underworld activity. It's the kind of expression you might expect to hear James Cagney use in some mobster film, although, as we shall see, the phrase isn't American.

Before tackling the origins of 'blow the gaff' we need to take a small detour to look at the places it was first recorded. There are a number of invaluable dictionaries that list and define the language of criminals and the underclasses and several of these play a part in deciphering where this phrase came from. In the UK the most notable of these are:

- A New Dictionary of the Terms Ancient and Modern of the Canting Crew, 1698.
- Francis Grose's 1785 edition of the Classical Dictionary of the Vulgar Tongue.

Also contributing to this story is an Australian dictionary, in fact the first dictionary ever compiled in Australia, The Memoirs of James Hardy Vaux including A Vocabulary of the Flash Language, 1819.

These titles need a bit of explaining in themselves. Cant is defined by the OED as "The secret language or jargon used by gipsies, thieves, professional beggars, etc. Any jargon used for the purpose of secrecy.". So the Canting Crew are those underworld characters and the dictionary defined how they spoke. And flash is defined as "Connected with or pertaining to the class of thieves, tramps, and prostitutes.", hence a dictionary of the flash language covered the same ground.

Now back to blow the gaff. There are several meanings of the word gaff and, to cut the story short, none of them are the direct source of 'blow the gaff'.

Another detour I'm afraid, to an earlier 18th century expression in use in the UK underworld - 'blow the gab'. This term had the same meaning, that is, 'to betray a confederate or reveal a secret'.

This phrase is first found in a doggerel poem which set down the code of 'honour amongst thieves' entitled The Oath Of The Canting Crew, first put into print by Robert Goadby in 1749:

I, Crank Cuffin, [a rogue] swear to be
True to this fraternity;
That I will in all obey
Rule and order of the lay.
Never blow the gab or squeak; [reveal secrets]
Never snitch to bum [bailiff] or beak [magistrate]

Francis Grose was good enough to include a definition of the term in his dictionary in 1785:

TO BLOW THE GAB, to confess, or peach. [inform on]

One of the meanings of gaff mentioned above is 'blasphemous or ribald speech'. It seems highly likely that that Old English meaning of gaff and the 18th century 'blow the gab' combined in some 19th century mind to become 'blow the gaff'.

The first printed example that I know of is from 1819, in James Vaux's dictionary referred to above:

BLOW THE GAFF, a person having any secret in his possession, or a knowledge of any thing injurious to another, when at last induced from revenge, or other motive, to tell it openly to the world and expose him publicly, is then said to have blown the gaff upon him.

Vaux was British by birth and was well acquainted with the language of the criminal classes. He was an inveterate thief and swindler and was transported to Australia as a convict in 1801.

Many of the early examples of 'blow the gaff' in print come from Australia. Whether Vaux was the person who migrated 'blow the gab' to 'blow the gaff' or whether the expression migrated with him from England we can't now be sure.

See other phrases recorded by Captain Francis Grose.