black tea vs tea leaf

black tea

noun
  • Tea leaves which have been "fermented" (actually, oxidized) before drying to enhance their flavour (cf. green tea). 

  • A cup of tea served without milk. 

tea leaf

noun
  • A dried fragment of a leaf of the tea plant used in making the drink tea. 

  • A thief. 

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