According to Wikipedia, “The term originates in the systematic psychological manipulation of a victim by her husband in the 1938 stage play Gaslight, known as Angel Street in the United States, and the film adaptations released in 1940 and 1944. In the story, a husband attempts to convince his wife and others that she is insane by manipulating small elements of their environment and insisting that she is mistaken, remembering things incorrectly, or delusional when she points out these changes. The play’s title alludes to the dimming of the gas lights in the house while the husband was using the gas lights in the sealed-off attic to search for jewels belonging to a woman whom he had murdered. The wife complains about the dimming lights to her husband, but he insists that she merely imagined it”
Below is the actual full Film Gaslight released in 1944. Enjoy!