Pork scratchings originated in the early 19th century, when the production of meat began to be industrialised. The term literally denotes the scraps from the slaughterhouse floor, lovely! With food scarce no part of the pig was wasted and either by design or by trial & error the famous Pork Scratching was discovered.
The consensus of opinion is that they originated in the West Midlands or Black Country. The Black Country is named after its roots in the industrial revolution and continuing role as a centre of heavy engineering and mining which in days gone by was said to cover the area in grime and soot.
It would seem that Pork Scratchings were very much a food of the working classes with origins back in the 1800's when it was produced as part of the tradition of families keeping their own pig at home and feeding it up for slaughter.