coitus interruptus vs onanism

coitus interruptus

noun
  • Sexual intercourse interrupted by withdrawal of the penis before ejaculation. 

onanism

noun
  • Ejaculating outside the vagina during intercourse; (the performing of) coitus interruptus. 

  • Masturbation. 

How often have the words coitus interruptus and onanism occurred in a corpus of books? (source: Google Ngram Viewer )