weathercock vs weathervane

weathercock

noun
  • A weather vane, sometimes in the form of a cockerel. 

  • A kind of wind pump whose top behaves like a weather vane, moving with the wind direction, but which also has a wheel attached to measure wind speed. 

  • One who veers with every change of current opinion; a fickle, inconstant person. 

verb
  • To act as a weathercock for. 

  • To turn upwind because of the difference in water pressure on two sides. 

  • To veer into the direction of the oncoming (relative) wind. 

weathervane

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