chancroid vs sexually transmitted disease

chancroid

noun
  • A sexually transmitted infection, caused by bacteria of species Haemophilus ducreyi, characterized by painful sores on the genitalia. 

  • A sore characteristic of this infection. 

sexually transmitted disease

noun
  • Any of various diseases that are usually contracted through sexual contact. 

How often have the words chancroid and sexually transmitted disease occurred in a corpus of books? (source: Google Ngram Viewer )