firm vs relentless

firm

adj
  • Steadfast, secure, solid (in position) 

  • Durable, rigid (material state) 

  • Fixed (in opinion). 

  • Insistent upon something, not accepting dissent. 

verb
  • To become firm; stabilise. 

  • To make firm or strong; fix securely. 

  • To improve after decline. 

  • To make compact or resistant to pressure; solidify. 

  • To shorten (of betting odds). 

  • To select (a higher education institution) as one's preferred choice, so as to enrol automatically if one's grades match the conditional offer. 

noun
  • A criminal gang, especially based around football hooliganism. 

  • A business partnership; the name under which it trades. 

  • A business enterprise, however organized. 

relentless

adj
  • Unremitting, steady and persistent. 

  • Unrelenting or unyielding in severity. 

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