baking powder vs barm

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. 

barm

noun
  • Foam rising upon beer, or other malt liquors, when fermenting, and used as leaven in making bread and in brewing; yeast. 

  • A small, flat, round individual loaf or roll of bread. 

verb
  • To spurge; foam 

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