A vernacular used by miners in the north-east of England.
Its name is hardly known even in the area in which it was once best known, though it has received attention from dialectologists and was featured in Melvyn Bragg's The Routes of English BBC Radio 4 series back in 2000. It has been in the news recently as a result of the publication of a book on it by Bill Griffiths.
It was the language of colliers and pitmen, miners in the coal seams of Durham and Northumberland, once the capital of coal (not for nothing was the saying "carrying coals to Newcastle" coined to refer to a useless undertaking). It has gradually died out as the deep pits of the area have progressively closed. Pitmatic is full of mining terms: "at bank", on the surface; "cavil", to choose your underground coal hewing station by lot; "hoggers", footless socks that made it easy to clean coal from between the toes, later a type of flannel drawers; "cracket", a stool on which a pitman sat while hewing coal; "kenner", the end of the shift; and "arse-flap", a loop attached to the winding rope in a shaft on which a man sat while carrying out repairs. Many of the terms can be traced back to Scots, Old Norse and Low German.
Trying to classify it isn't so easy. It isn't a dialect, because it is mainly vocabulary, lacking grammatical features that separate it from other types of speech (the main dialect of the area is the one commonly called Geordie). It isn't just a workplace jargon, though that's where it comes from, because some of the terms have escaped into the wider community, such as "greaser", a device to lubricate the wheels of the coal tubs, which led to the expression "gan canny ower (go carefully over) the greaser", meaning "mind how you go"; It can't be called an argot, which is a semi-secret vocabulary with criminal associations, or a patois, which is a low-status dialect, which Pitmatic certainly wasn't. Call it a vernacular.
The term is first recorded in print, in a slightly different form, in an article in The Newcastle Weekly Chronicle back in 1873:
A great many of the lads, especially from the Durham district, had evidently never been in Newcastle previously, and the air of wonder with which they gazed at the crowds, at the buildings, and especially at the fine folks who occupied the windows, was very amusing. If the quality criticized and quizzed them, the lads returned the compliment, and it was entertaining enough to catch snatches of criticism on the manners and customs of the upper ten thousand of Newcastle, reduced to the purest "pitmatical", shouted across the streets, as the men and lads belonging to collieries swept by where I stood in the crowd...
That fuller form, "Pitmatical", soon abbreviated, gives the clue to its origin. It's a compound of "pit" and "mathematical", which may have been intended to stress the skill, precision and craft of the colliers' work."
[Pitmatic: The Talk of the North East Coalfield, is published by Northumbria University Press, £9.99. ISBN 1-904794-25-4. The book goes well beyond vocabulary to include many examples of songs and stories written in Pitmatic by colliers about pit life and shows how the speech fitted into the wider language-world of the region.]