bittersweet vs horse chestnut

bittersweet

noun
  • A vine, of the genus Celastrus, having small orange fruit that open to reveal red seeds. 

  • A pinkish-orange color. Any color in between scarlet and orange. 

  • Bittersweetness. 

  • Bittersweet nightshade, Solanum dulcamara. 

  • Any variety of clam in the family Glycymerididae 

  • A variety of apple with a bittersweet taste. 

adj
  • Both bitter and sweet. 

  • Expressing contrasting emotions of pain and pleasure. 

  • Of bittersweet color. 

horse chestnut

noun
  • The large nutlike seed of these trees. 

  • Any of several tree species of genus Aesculus, especially Aesculus hippocastanum, common in temperate northern hemisphere. 

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