baking powder vs leavening

baking powder

noun
  • A dry leavening agent used in baking; a mixture of baking soda, an acid (often cream of tartar) and starch to keep it dry; when wetted, carbon dioxide is released. 

leavening

noun
  • The process by which something is leavened. 

  • Synonym of leavening agent 

adj
  • Making light by aeration. 

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