assay vs beat a dead horse

assay

verb
  • To attempt (something). 

  • To affect. 

  • To analyze or estimate the composition or value of (a metal, ore etc.). 

  • To try tasting, as food or drink. 

noun
  • Tested purity or value. 

  • Trial, attempt. 

  • The qualitative or quantitative chemical analysis of something. 

  • The act or process of ascertaining the proportion of a particular metal in an ore or alloy; especially, the determination of the proportion of gold or silver in bullion or coin. 

  • The alloy or metal to be assayed. 

  • Examination and determination; test. 

  • Trial by danger or by affliction; adventure; risk; hardship; state of being tried. 

beat a dead horse

verb
  • To persist or continue far beyond any purpose, interest or reason. 

How often have the words assay and beat a dead horse occurred in a corpus of books? (source: Google Ngram Viewer )