crackdown vs retardant

crackdown

noun
  • Abruptly stern measures or disciplinary action; increased enforcement 

retardant

noun
  • Something that serves to retard (slow down) the action of something 

adj
  • Serving to impede (slow down) the action of something 

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