clampdown vs retardant

clampdown

noun
  • A sudden repressive or punitive restriction or control 

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 clampdown and retardant occurred in a corpus of books? (source: Google Ngram Viewer )