mainstay vs stalwart

mainstay

noun
  • A chief support. 

  • Someone or something that can be depended on to make a regular contribution. 

  • A stabilising rope from the top of the mainmast to the bottom of the foremast. 

stalwart

noun
  • One who firmly supports a cause. 

  • One who is dependable. 

  • One who has a strong build. 

adj
  • Firmly or solidly built. 

  • Courageous. 

  • Determined; staunch. 

How often have the words mainstay and stalwart occurred in a corpus of books? (source: Google Ngram Viewer )