Charles Boyer and Ingrid Bergman in director George Cukor’s 1944 film “Gaslight” — a term that has now become a buzzword in psychology and politics. (Silver Screen Collection/Getty Images)

She hears footsteps from above, shuffling against the attic floorboards. A framed painting suddenly vanishes from a wall. The gas-fueled flames of the chandelier flicker and dim.

She is certain it happened — but her husband assures her that she’s imagining it all. It’s her behavior that seems odd, he insists; perhaps she’s going mad? And, slowly, she begins to believe him.

This is the plot of the 1944 Ingrid Bergman film “Gaslight.” It is also the origin of a buzzword that has spread from pop culture to clinical psychology and back again — but has never been more visible than it is now, in commentary about the conduct of President Trump:

CNN: Donald Trump is ‘gaslighting’ all of us

Teen Vogue: Donald Trump Is Gaslighting America

NBC: Some Experts Say Trump Team’s Falsehoods Are Classic ‘Gaslighting’

This is a very specific accusation. To “gaslight” someone isn’t just to lie to them or to manipulate their emotions. It is a deliberate attempt to deceive someone into questioning their own perception of reality. (“Suddenly, I’m beginning not to trust my memory at all,” says Bergman’s character, Paula, as her faith in her senses begins to fray.)

Throughout Trump’s ascent to the presidency, he was repeatedly accused of this sort of ma­nipu­la­tion. When he wanted to shift attention away from his vocal support of the birther movement, he falsely claimed that Hillary Clinton had started the conspiracy theory. Trump told the New York Times that it was a “mistake” for him to retweet an unflattering photo of Ted Cruz’s wife — then later insisted in a TV interview, “I didn’t actually say it that way.” He vehemently denied that he had mocked a disabled reporter, despite a widely circulated video that showed him doing exactly that. After winning the election by a narrow margin, losing the popular vote by nearly 3 million, Trump hailed his victory as a “landslide.” Most recently, Trump and his administration have insisted that the crowd at his inauguration was the largest in American history — even as aerial photographs, crowd estimates, Metro ridership numbers and witnesses on the scene show otherwise.

Naveen Joshi, a professor of cultural studies at Humber College in Toronto, isn’t surprised that commentators have assigned a clinical label to Trump’s tendencies. “Gaslighting” was adopted by psychologists after the movie, which was based on a 1938 play.

But “with the rise of people talking about mental health, you see people using these terms more effectively now,” well beyond professional settings, Joshi says. “And especially with online social networking, they can circulate like wildfire.”

The idea of a malevolent force messing with your mind is deeply embedded in our popular fiction — “a central plot point,” Joshi says.

Long-running soap operas such as “Guiding Light” were among the first to seize on the concept, he says. “Victor Newman is constantly gaslighting his children in ‘The Young and the Restless’ to convince them that the problems with the family are their fault and not his.”

Jack Nicholson’s character in “The Shining” tries to convince his wife that she is overreacting to alarming occurrences in a haunted hotel. In Showtime’s “Homeland,” Claire Danes’s character is gaslighted by enemy operatives who swap her bipolar medication and send her spiraling into a full-blown breakdown. The HBO drama “Westworld” is centered on an entire race of androids who have their memories controlled and repeatedly wiped clean by human overlords. In last year’s thriller “The Girl on the Train” — spoiler alert — gaslighting was an essential part of the film’s climactic plot twist.

These sorts of stories resonate, Joshi says, because they reveal just how easy it is for people to become disoriented, “especially when they’re vulnerable,” he says. “It speaks to how helpless we are when we’re screaming for information and we don’t know whether it’s true or not.”

But it wasn’t until 10 or 15 years ago that the term itself became popular, popping up frequently in advice columns or news stories about domestic violence.

“As is common with people who mistreat others,” Washington Post advice columnist Carolyn Hax told a troubled reader in 2013, “your partner responded by blaming you and apparently gaslighting you off to therapy.”

(Obtained by The Washington Post)

Until recently, it was rare to see the word used in a political context — though in a 1995 New York Times column, Maureen Dowd argued the Clinton administration was “gaslighting” then-House Speaker Newt Gingrich by needling him with minor slights. (She predicted it wouldn’t work: “In the movie, the husband tried to make the wife unstrung because she wasn’t unstrung. You can’t Gaslight someone who is already a little lit.”)

It wasn’t until late 2015 that we began to see “gaslighting” applied to Trump. Among the first to do so was conservative pundit Matt K. Lewis, in a November 2015 article for the Telegraph: “Any introspective person covering Mr Trump will eventually have to grapple with whether or not they want to believe The Donald or their lying eyes.”

And then, even some psychologists took up the idea, drawing parallels between Trump’s actions and the classic tricks of gaslighting — such as undermining the victim’s perspective, controlling the topic of conversation and forcefully denying the truth.

Leah McElrath, a psychotherapist and political activist, analyzed Trump’s quasi-apology after the release of the notorious “Access Hollywood” video in which he made vulgar comments bragging about assaulting women.

Trump’s insistence that “these words do not reflect who I am” amounted to gaslighting, McElrath wrote — similar to the language she’s heard from domestic abusers — effectively telling the public that “the reality you just experienced didn’t actually happen.” (Her Twitter thread on the subject was retweeted thousands of times.)

Fortunately, some of our gaslighted heroines from fiction offer tips on how to break free of the cycle, Joshi says.

“Either it becomes so evident that something is wrong” — as in “The Shining,” where blood pouring out of the elevator is hard to ignore — “or you need a witness, someone who is there to help you through it and point it out,” he says.

But as “gaslighting” slips into common parlance, he worries we’re not always using it correctly: “It ends up getting flattened, and it begins to mean nothing.” Gaslighting does not apply to every type of deceptive behavior, he says — even if he would argue that it’s been fairly applied to Trump in some cases.

“It’s quite obvious to see that there’s some form of manipulation going on,” Joshi says. “We’re going to have to read ourselves out of it. We need multiple sources. We should be critical of everything — even the word ‘gaslighting’ itself.”