footmarks vs slipstream

footmarks

slipstream

verb
  • To take advantage of the suction produced by a slipstream by travelling immediately behind the slipstream generator. 

  • To incorporate additional software (such as patches) into an existing installer. 

noun
  • A generated advantage which makes forward movement easier. 

  • A genre of fantastic or non-realistic fiction that crosses conventional genre boundaries. 

  • The low-pressure zone immediately following a rapidly moving object, caused by turbulence. 

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