rack off vs scat

rack off

verb
  • To go away; to sod off. 

  • Used other than figuratively or idiomatically: see rack, off. 

scat

verb
  • To leave quickly. 

  • Here comes the principal; we'd better scat. 

  • To sing an improvised melodic solo using nonsense syllables, often onomatopoeic or imitative of musical instruments. 

noun
  • A tax; tribute. 

  • Animal excrement; droppings, dung. 

  • Coprophilia. 

  • Heroin. 

  • Any fish in the family Scatophagidae 

  • A land-tax paid in the Shetland Islands. 

  • A brisk shower of rain, driven by the wind. 

  • Scat singing. 

intj
  • An imperative demand to leave, often understood by speaker and listener as impertinent. 

  • Scat! Go on! Get out of here! 

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