grist for the mill vs guerdon

grist for the mill

noun
  • Something that is useful or that creates a favorable opportunity. 

guerdon

noun
  • A reward, prize or recompense for a service; an accolade. 

verb
  • To give such a reward to. 

How often have the words grist for the mill and guerdon occurred in a corpus of books? (source: Google Ngram Viewer )