You’ve probably heard the phrase ‘to add grist to the mill’, meaning to use something to your advantage e.g. ‘his utter stupidity really added grist to the mill’. But what exactly is grist? And why are you adding it to your mill? Well, it turns out that it’s a pretty literal metaphor – grist is simply grain that’s ground into flour and a mill is, well, you know what a mill is.
A mill, obviously
The earliest known use of the phrase in the metaphorical sense is in a work by an English theologian and reformer called John Foxe, who wrote in 1570: ‘All these are as grist to the mill to the papists.’ You might be able to guess from this that Foxe was a protestant, having converted from Catholicism. If I were a cynic, I might think that some of the reason for this was because he was due to take Catholic holy orders after his academic career ended, which of course meant giving up all action in the trouser department. He went on to have six kids, so it was lucky for them he did convert. Although Wikipedia describes him as ‘so bookish that he ruined his health by his persistent study’, so I’m very impressed he found the time. He also wrote an enormous (1,800 pages no less) history of Christian martyrs and their persecution and suffering, which became a popular and influential work during the Protestant Reformation, so maybe it wasn’t all about the winkie.
Anyway, back to ‘grist’. It comes from the Old English word, ahem, ‘grīst’, which also means ‘ground grain’. Not much of an etymological leap there then. That comes from the Old High German word ‘grist’ (again), the Middle Low German word ‘grêst’ (we’re mixing it up now) and the Old Norse word ‘grysta’ (woop woop), all of which mean, you’ve guessed it, ‘ground grain’. ‘Grist’ is also where we get ‘grind’ from. (Are you still awake?)
We’ve been using the word ‘grist’ in English since at least the 9th century to refer to both the grain brought to a mill for grinding, and the ground flour itself (which seems confusing to me, so lucky I’m not a miller).