assist vs double-cross

assist

verb
  • To help. 

  • To make a pass that leads directly towards scoring. 

  • To help compensate for what is missing with the help of a medical technique or therapy. 

noun
  • A decisive pass made to the goal scorer 

  • A helpful action or an act of giving. 

  • A defensive play, allowing a teammate to record a putout. 

double-cross

verb
  • To betray or go back on. 

  • To cross twice in hybridization, as (A × B) × (C × D); for example, in commercial hybrid seed corn, A through D are classically inbreds, and their grandoffspring is the seed for sale. 

How often have the words assist and double-cross occurred in a corpus of books? (source: Google Ngram Viewer )