caw vs knell

caw

noun
  • The harsh cry of a crow. 

verb
  • To make the harsh cry of a crow, rook, or raven. 

intj
  • A rendering of the vocalisation of a crow or other corvid. 

knell

noun
  • The sound of a bell knelling; a toll (particularly one signalling a death). 

  • A sign of the end or demise of something or someone. 

verb
  • To ring a bell slowly, especially for a funeral; to toll. 

  • To signal or proclaim something (especially a death) by ringing a bell. 

  • To summon by, or as if by, ringing a bell. 

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