carol vs vocative

carol

noun
  • A ballad or song of joy. 

  • A (usually traditional) religious or secular song sung at Christmastime. 

  • A round dance accompanied by singing. 

verb
  • To sing carols; especially to sing Christmas carols in a group. 

  • To praise or celebrate in song. 

  • To sing in a joyful manner. 

  • To sing (a song) cheerfully. 

  • To participate in a carol (a round dance accompanied by singing). 

vocative

noun
  • Something said to (or as though to) a particular person or thing; an entreaty, an invocation. 

  • The vocative case 

  • A word in the vocative case 

adj
  • Of or pertaining to calling; used in calling or vocation. 

  • Used in address; appellative (said of that case or form of the noun, pronoun, or adjective, in which a person or thing is addressed). For example "Domine, O Lord" 

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