croup vs rusty dusty

croup

noun
  • An infectious illness of the larynx, especially in young children, causing respiratory difficulty. 

  • The top of the rump of a horse or other quadruped. 

rusty dusty

noun
  • The buttocks of someone who sits and does nothing. 

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