national anthem vs refrain

national anthem

noun
  • The official song of a constituent state of a country. 

  • The official song of a nation or sovereign state, generally of a patriotic nature and played at events to celebrate or honor said state. 

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). 

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