In the film Gaslight (1944), Charles Boyer plays tricks on his wife (Ingrid Bergman) to make her think she is crazy, so he can have her committed to an asylum and find some jewels hidden in her house. Alex Good, at Alex on Film, prefers the less-well-known 1940 version:
In 1944 MGM managed to get a bunch of stars in alignment (and it wasn’t easy), but I prefer Anton Walbrook [in the 1940 film] to Charles Boyer. Walbrook is a more believable and altogether nastier piece of work. His creepy voice has an unnerving way of making his lines sound a bit like perverted baby-talk. And while it will be accounted heresy by some, I think Diana Wynyard is more convincing in the role of the bride coming unglued than the always composed Ingrid Bergman. Wynyard has the haunted, neurotic look of Véra Clouzot in Les Diaboliques, or Mia Farrow in Rosemary’s Baby. Finally, the amateur sleuth/hostler Frank Pettingell is a lot more fun than Joseph Cotten (“Saucy shirt, isn’t it?”), and Cathleen Cordell is a more erotic housemaid than Angela Lansbury, without having to try so hard. There’s some real heat generated between her and her louche master.
In the comments we discuss the term "gaslighting." The Maddow mafia evidently thinks Trump invented it but it was slung around quite a bit in the Bush II era. Good notes that Maureen Dowd even applied it to Bill Clinton, in the 1990s. How long has the verb "to gaslight" been around? One article traces it as far back as the 1960s TV show Gomer Pyle USMC:
Here’s an example of the verb “gaslight” in “The Grudge Match,” an episode that aired on 12 Nov. 1965 (antedating OED’s 1969 cite for the verb, as well as the Dec. 1965 cite for the verbal noun).
Duke: You know, you guys, I’m wondering. Maybe if we can’t get through to the sarge we can get through to the chief.
Frankie: How do you mean?…
Duke: The old war on nerves. We’ll gaslight him.
In addition to being a hoary cliche of political discussion, "gaslighting" has also been embraced by the therapy community. Search the term and you'll pull up many articles with titles such as "12 Signs You Are Being Gaslighted by a Narcissist." (Shouldn't that be gaslit?)
But for all its cliche-dom, repetition, and use as a Trump-cudgel, what does the term even mean? Politically, it seems to have devolved from “employing elaborate ruses to make a person think he or she is crazy” to merely “scaring people or psych-ing them out.” As a therapy trope its connection to the film(s) is tenuous. Most spouse abuse is not predicated on a calculated program of deceptions for material gain, it's just the guy being an a-hole. Both the pundits and the shrinks make the term mean what they want it to mean. They are, y'know, gaslighting us.