interlock vs mortise

interlock

verb
  • To interlace. 

  • To fit or clasp together securely. 

noun
  • A safety device that prevents activation in unsafe conditions. 

mortise

verb
  • To join by a mortise and tenon. 

  • To adjust the horizontal space between selected pairs of letters; to kern. 

  • To cut a mortise in. 

noun
  • A hole that is made to receive a tenon so as to form a joint. 

  • Stability; power of adhesion. 

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