clank vs hmm

clank

verb
  • To make a clanking sound 

  • To cause to sound with a clank. 

noun
  • A loud, hard sound of metal hitting metal. 

hmm

verb
  • To make a thoughtful humming noise. 

intj
  • A demand for an answer to a question. 

  • Indicating thinking or pondering. 

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