reservoir vs waterhole

reservoir

noun
  • A large natural or artificial lake used as a source of water supply. 

  • A species that acts as host to a zoonosis when it is not causing acute illness in other susceptible species. 

  • A "black box" component that receives an input signal to be read out and mapped by another process, as part of reservoir computing. 

  • A small intercellular space, often containing resin, essential oil, or some other secreted matter. 

  • A supply or source of something. 

  • A place where anything is kept in store. 

verb
  • To store or keep (something) in or as in a reservoir. 

waterhole

noun
  • A depression in which water collects, especially one where wild animals come to drink. 

  • A watering hole; a place where people meet to drink and talk. 

  • A part of the electromagnetic spectrum, between the regions where hydrogen and hydroxyl radiate, that is relatively quiet in terms of radio astronomy. 

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