chancroid vs soft chancre

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. 

soft chancre

noun
  • chancroid (sexually transmitted disease) 

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