In 1938, a Victorian-era thriller titled Gas Light opened in London. The play, which was titled Angel Street in the United States, is about a husband who attempts to drive his young wife mad by causing her to doubt her own grip on reality. Its title alludes to the dimming of the gaslights in the house when the husband uses the lights in the attic while searching for hidden jewels. When the wife tells her husband about the dimming lights as well as the accompanying noises upstairs, he insists that she is imagining things and leads her to believe that she is going insane.
The play was made into a movie in 1944, starring Charles Boyer as the villainous husband and Ingrid Bergman as the distraught wife. The film version apparently prompted the use of gaslight as a verb meaning "to attempt to make (someone) believe he or she is going insane." The Historical Dictionary of American Slang has a record of use in a speech from 1956 in which a woman defines gaslight in a way that reflects the above definition and gives its source as being the movie. The term is commonly used today as a verb and verbal noun.
With doors opening when they're not supposed to and strange messages appearing on computer screens, Claire gets nothing but gaslighted….
— Susannah Breslin, Film Threat, 22 Jul. 2000
Then her psychiatrist (Gary Sinise) and her husband (Anthony Edwards) tell her she never had a son—she imagined young Sam, manufactured nine years of memories. The movies, clippings and photographs vanish. Is Telly bonkers or are they gaslighting her?
— Eric Harrison, The Houston Chronicle, 24 Sept. 2004
Gaslighting, one of the most psychologically damaging types of harassment, is when serial abusers present false information or a false narrative to make you doubt your own memory, perceptions, sanity, or professional knowledge.
— Anita Sarkeesian, Marie Claire, 1 Mar. 2015