metronome vs pendulum

metronome

noun
  • A device, containing an inverted pendulum, used to mark time by means of regular ticks at adjustable intervals; an electronic equivalent that emits flashes. 

pendulum

noun
  • A body suspended from a fixed support so that it swings freely back and forth under the influence of gravity, commonly used to regulate various devices such as clocks. 

  • A watch's guard-ring by which it is attached to a chain. 

  • Used to refer to the tendency of a situation to oscillate (between two extremes). 

  • A lamp, etc. suspended from a ceiling. 

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