extension cord vs rectifier

extension cord

noun
  • An electrical cord with a plug one end, and a single socket or a multi-port socket at the other end, used for powering one or more devices at a distance, too far from the wall outlet to be reached by the normal cords of the device or devices. 

rectifier

noun
  • A device that converts alternating current into direct current; often a diode. 

  • The activation function f(x)= max (0,x), where x is the input to a neuron. 

  • An instrument used for determining and rectifying the variations of the compass on board ship. 

  • Something that rectifies. 

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