To work, study, or practice hard and steadily. To persist in an unpleasant task; to labor continuously, especially at hard, monotonous work.
There are two types of grindstones. One is used to grind grain and is called a millstone. The other is used for shaping, smoothing, and sharpening metal, including dull knife blades and axes, and is called a grindstone.
There are also two theories about where the phrase ‘keep one’s nose to the grindstone’ came from. One is that it came from the purported habit of millers, who had to check now and again that the millstones weren’t overheating, by putting their nose to the grindstone to see if they smelled any burning.
The evidence is quite definitely against this first theory. The stones used by millers were called millstones, not grindstones, as early as 1400. If the miller theory was correct, we would expect the phrase to be ‘nose to the millstone.’ In addition, a miller occasionally sniffing for burning between the stones does not provide a picture of hard, monotonous, and unpleasant work.
The second theory says that the phrase comes from the practice of grinders, when sharpening knife blades, to bend over the flat, circular stone which was upright, revolving on an axis. Shaping metal with a grindstone would have been hard work, requiring concentration, and would have been monotonous to boot. The task would also have been unpleasant, since metal shavings and stone dust would end up on the clothes and in the lungs of the worker.
This second theory appears to be correct one. Not only does it refer to hard, boring work, early citations refer to holding one’s nose to the grindstone as a form of punishment. One gets the feeling the worker was strapped to his bench.
The first known citation is John Frith’s A mirrour or glasse to know thyselfe, 1532.
‘Back to the grindstone’ means to resume work after a break. According to the Shorter Dictionary of Catch Phrases by Fergusson from the work of Partridge & Beale, this phrase has been in use since around 1830. Some people say, ‘back to the salt mines.’
On the homestead where I grew up, my father used a grindstone to sharpen axes and knives. My job was stand beside the grindstone and turn the handle for him, so I can testify to the fact that the work is monotonous and requires concentration. I was also required to occasionally pour a little water on the stone, but I don’t remember the reason for doing so. Perhaps to keep the stone cool?