titwank vs top surgery

titwank

noun

  • An act of masturbating the penis between one's breasts. 

verb

  • To masturbate the penis using one's breasts. 

top surgery

noun

  • Mastectomy. 

  • Breast augmentation. 

How often have the words titwank and top surgery occurred in a corpus of books? (source: Google Ngram Viewer )