guano vs sewage

guano

noun
  • Coccothrinax borhidiana, a variety of palm tree indigenous to Cuba. 

  • Dung from a sea bird or from a bat. 

sewage

noun
  • A suspension of water and solid waste, transported by sewers to be disposed of or processed. 

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