refrain vs usefulness

refrain

noun
  • The chorus or burden of a song repeated at the end of each verse or stanza. 

  • A much repeated comment, complaint, or saying. 

verb
  • To stop oneself from some action or interference; to abstain. 

  • To abstain from (food or drink). 

usefulness

noun
  • The quality or degree of being useful. 

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