leaven vs leavening agent

leaven

noun
  • Any agent used to make dough rise or to have a similar effect on baked goods. 

  • Anything that induces change, especially a corrupting or vitiating change. 

verb
  • To add a leavening agent. 

  • To cause to rise by fermentation. 

  • To temper an action or decision. 

  • To imbue; to infect; to vitiate. 

  • To rise or become larger. 

leavening agent

noun
  • Any organism or substance added to a food product (such as dough or batter) that makes it rise when cooked. 

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