outflow vs overburden

outflow

noun
  • Something that flows out of a sewage treatment plant. 

  • Any outward movement. 

  • The process of flowing out. 

  • A fluid that flows out. 

  • A stream of gaseous material emanating from an active galactic nucleus. 

  • The part of a system that allows material to flow out. 

verb
  • To flow outward. 

overburden

noun
  • A sterile stratum that lies above the stratum being investigated 

  • The rock and subsoil that lies above a mineral deposit such as a coal seam. 

verb
  • To overload or overtax. 

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