excretion vs secretion

excretion

noun
  • Something excreted in that manner, especially urine or feces. 

  • The process of removing or ejecting material that has no further utility, especially from the body; the act of excreting. 

secretion

noun
  • the act of secreting a substance, especially from a gland 

  • any substance that is secreted by an organism 

  • the act of hiding something 

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