lagoon vs waterhole

lagoon

noun
  • A shallow body of water separated from deeper sea by a bar. 

waterhole

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

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

  • 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 lagoon and waterhole occurred in a corpus of books? (source: Google Ngram Viewer )