thyratron
noun
thy·ra·tron ˈthī-rə-ˌträn 
: a gas-filled hot-cathode electron tube in which the grid controls only the start of a continuous current thus giving the tube a trigger effect
Word History
Etymology
Greek thýra "door" + -tron — more at door
Note: The American physicist and electrical engineer Albert W. Hull (1880-1966) is credited with coinage of this word and several other names of electron tubes (as magnetron) ; see C.G. Suits and J.M. Lafferty, Albert Wallace Hull, 1880-1966, A Biographical Memoir, National Academy of Sciences, Washington, D.C., 1970.
First Known Use
1929, in the meaning defined above