green tea vs tisane

green tea

noun
  • A beverage brewed from green tea leaves. 

  • Leaves of the tea plant which are treated with steam or roasted to denature the enzymes that cause the leaves to darken and change taste. (Without this step they would become oolong tea or black tea). 

tisane

noun
  • A medicinal drink, originally made from barley soaked in water. 

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