bop vs hard rock

bop

noun
  • A style of improvised jazz from the 1940s. 

  • A very light smack, blow or punch. 

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

  • 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. 

hard rock

noun
  • A rock music genre marked by a heavy regular beat, high amplification, and usually frenzied performances. 

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