extension cord vs trip cord

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. 

trip cord

noun
  • A cord, line, lanyard, or wire that, when pulled, mechanically activates a device. 

  • A type of electrical extension cord: see pad. 

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