R-rated vs XXXX

R-rated

adj
  • Not suitable for children, especially due to involving excessive sexual, violent, or rude content 

  • Of a motion picture, having an "R rating" from one more motion picture rating authorities, typically meaning it is suitable only for adults. 

  • Of a motion picture, having an "R rating" from the Motion Picture Association (MPA), meaning it is suitable only for adults. 

XXXX

adj
  • X-rated, pornographic 

name
  • a fuck / damn. 

  • Tetrasomy X, a rare chromosomal disorder affecting females, caused by the presence of four X chromosomes instead of two present in the usual human karyotype. 

How often have the words R-rated and XXXX occurred in a corpus of books? (source: Google Ngram Viewer )