gaslight vs thermionic valve

gaslight

noun
  • The light produced by the burning gas in such a lamp. 

  • A lamp which operates by burning piped illuminating gas (or town gas). 

verb
  • To manipulate someone such that they doubt their own memory, perceptions of reality, or sanity, typically for malevolent reasons. 

thermionic valve

noun
  • An electronic device incorporating electrons from a glowing cathode inside an evacuated glass tube, functioning as a switch, amplifier etc. 

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