ache vs clonus

ache

noun
  • Continued dull pain, as distinguished from sudden twinges, or spasmodic pain. 

verb
  • To cause someone or something to suffer pain. 

  • To suffer pain; to be the source of, or be in, pain, especially continued dull pain; to be distressed. 

clonus

noun
  • A muscular spasm with regular contractions. 

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