heat of passion vs trigger point

heat of passion

noun
  • An outburst of anger that leads one to commit a criminal act, and is itself influenced by preceding events that might cause a reasonable person to lose self control. 

trigger point

noun
  • An event, arrangement, provocation, etc. that leads a certain, generally violent or angered, action to be taken. 

  • A hyperirritable spot in the skeletal muscle; a point in tender muscle that tends to elicit pain upon pressure or touch. ᵂᵖ 

How often have the words heat of passion and trigger point occurred in a corpus of books? (source: Google Ngram Viewer )