thrush vs true thrush

thrush

noun
  • Any of numerous species of songbirds of the cosmopolitan family Turdidae, such as the song thrush, mistle thrush, bluebird, and American robin. 

  • A female singer. 

  • A fungal infection caused by Candida, now especially of the vagina; candidiasis. 

true thrush

noun
  • Any member of the genus Turdus. 

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