come to a stop vs slacken

come to a stop

verb
  • To reach a point where little progress is being made; to come to an impasse; to stop. 

  • To stop moving or being active; to stop. 

slacken

verb
  • To gradually decrease in intensity or tautness; to become slack. 

  • To make slack, less taut, or less intense. 

  • To deprive of cohesion by combining chemically with water; to slake. 

How often have the words come to a stop and slacken occurred in a corpus of books? (source: Google Ngram Viewer )