earth vs rock music

earth

noun
  • Any general rock-based material. 

  • The people on the globe. 

  • The lair or den (as a hole in the ground) of an animal such as a fox. 

  • A region of the planet; a land or country. 

  • Any planet similar to the Earth (our earth): an exoplanet viewed as another earth, or a potential one. 

  • A connection electrically to the earth ((US) ground); on equipment: a terminal connected in that manner. 

  • The ground, land (as opposed to the sky or sea). 

  • Soil. 

  • The world of our current life (as opposed to heaven or an afterlife). 

  • The aforementioned soil- or rock-based material, considered one of the four or five classical elements. 

  • Worldly things, as against spiritual ones. 

verb
  • To hide, or cause to hide, in the earth; to chase into a burrow or den. 

  • To bury. 

  • To burrow. 

  • To connect electrically to the earth. 

rock music

noun
  • A broad genre of popular music, including especially those styles ultimately derived from rock and roll, employing electrical amplification, heavy use of guitars, 4/4 time with strong percussive rhythm on beats two and four (backbeat), and usually themes of bold wildness, rebellion, and sexuality. 

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