onanism vs tug

onanism

noun
  • Masturbation. 

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

tug

noun
  • An act of male masturbation. 

  • A dog toy consisting of a rope, often with a knot in it. 

  • A trace, or drawing strap, of a harness. 

  • A tugboat. 

  • An iron hook of a hoisting tub, to which a tackle is affixed. 

  • A sudden powerful pull. 

verb
  • To masturbate. 

  • To tow by tugboat. 

  • To pull or drag with great effort. 

  • To pull hard repeatedly. 

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