kick-off vs onset

kick-off

noun
  • The opening sequence of notes in a song, usually played by the song's main instrument, to indicate the beginning of the song. 

  • The opening kick of each half of a game of football. 

  • The opening sequence of any event. 

onset

noun
  • The beginning of a musical note or other sound, in which the amplitude rises from zero to an initial peak. 

  • The initial portion of a syllable, preceding the syllable nucleus. 

  • The initial phase of a disease or condition, in which symptoms first become apparent. 

  • A setting about; a beginning. 

How often have the words kick-off and onset occurred in a corpus of books? (source: Google Ngram Viewer )