sky vs waterfall

sky

verb
  • To drink (a beverage) from a container without one's lips touching the container. 

  • To move quickly, as if by flying; to fly; also, to escape, to flee (especially by airplane). 

  • To hit, kick, or throw (a ball) extremely high. 

  • To clear (a high jump bar, hurdle, etc.) by a large margin. 

  • To hit, kick, or throw a ball extremely high. 

  • To raise an oar too high above the water. 

noun
  • The atmosphere above a given point, especially as visible from the surface of the Earth as the place where the sun, moon, stars, and clouds are seen. 

  • With a descriptive word: the part of the sky which can be seen from a specific place or at a specific time; its climate, condition, etc. 

  • The set of all lightlike lines (or directions) passing through a given point in space-time. 

waterfall

verb
  • To drink (something) from a container by pouring it from a height so as not to touch one's lips to the rim. 

  • To fall like a waterfall. 

  • Synonym of recycle 

noun
  • A waterfall-like outpouring of liquid, smoke, etc. 

  • A flow of water over the edge of a cliff. 

  • Waterfall model 

  • The action of drinking from a vessel without touching it with the lips, considered more sanitary for a shared vessel. 

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