struggle vs tug

struggle

noun
  • A contortion of the body in an attempt to escape or to perform a difficult task. 

  • Strife, contention, great effort. 

verb
  • To strive, to labour in difficulty, to fight (for or against), to contend. 

  • To strive, or to make efforts, with a twisting, or with contortions of the body. 

tug

noun
  • A sudden powerful pull. 

  • 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. 

  • An act of male masturbation. 

verb
  • To masturbate. 

  • To tow by tugboat. 

  • To pull or drag with great effort. 

  • To pull hard repeatedly. 

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