throttle vs vacuum tube

throttle

noun
  • The lever or pedal that controls this valve. 

  • A valve that regulates the supply of fuel-air mixture to an internal combustion engine and thus controls its speed; a similar valve that controls the air supply to an engine. 

verb
  • To utter with breaks and interruption, in the manner of a person half suffocated. 

  • To have the throat obstructed so as to be in danger of suffocation; to choke; to suffocate. 

  • To control or adjust the speed of (an engine). 

  • To breathe hard, as when nearly suffocated. 

  • To cut back on the speed of (an engine, person, organization, network connection, etc.). 

  • To strangle or choke someone. 

vacuum tube

noun
  • A type of electron tube that controls electron current through vacuum between electrodes within a sealed container, usually of glass or metal and often designed to be easily installed in and removed from the equipment in which it is used. 

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