In my earlier posting on my grandfather's article I should have perhaps explained the term "printer's devil" which appears there. It refers to a printer's apprentice. The following (taken from an unpublished autobiographical note by my grandfather) gives an idea of what it was like to be a printer's devil in the first half of the last century:
Walter Brelstaff went to Providence Infants' School in 1908, afterwards to Northgate School which he left in 1916 to start work as an errand boy a J. T. Stokeld & Sons, local printers. He was for some time a real printer's devil, having to wash the large and small composition rollers used for automatic inking on the presses. There were three machines for printing larger sizes of paper and two smaller machines. It was a very dirty job, using paraffin to remove the ink. A black apron was poor protection. It was some time before he could get rid of the soreness and traces of ink. There was only a cold tap to wash hands. The large lead-lined sink was also used for washing type taken of the presses. Paraffin again. A large thick board sloped down into the sink to support the 'formes' - iron and steel frames into which the type was securely locked.
On the web you will find several very fanciful, contrived and almost certainly incorrect derivations proposed for the term "printer's devil". It most probably comes from the common use of "devil" to refer to a dirty or mischievous child. My guess is that it originated back in the Middle Ages, probably fairly soon after Caxton introduced the printing press to England.