bop vs heavy metal

bop

noun
  • A very light smack, blow or punch. 

  • A party hosted by a college's JCR or MCR. 

  • A style of improvised jazz from the 1940s. 

  • A good song. 

verb
  • To walk the streets while socializing. 

  • To dance to this music, or any sort of music with a marked beat. 

  • To have sex. 

  • To strike gently or playfully. 

  • To fellate. 

heavy metal

noun
  • guns or shot of large size. 

  • A genre descended from rock music, characterized by massive sound, highly amplified distortion, and overall loudness, often with extended guitar solos, and lyrics that involve aggressive or fantastic imagery. 

  • Any metal that has a specific gravity greater than about 5, especially one, such as lead, that is poisonous and may be a hazard in the environment. (There are many different definitions of what counts as a heavy metal; see Heavy metals for a discussion.) 

  • Great influence or power. 

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