Gaslighting
Etymology
From the 1938 play Gas Light (and its 1944 film), in which a husband secretly dims the gas lamps and then insists his wife is imagining the change, to make her think she’s losing her mind. The title became a verb. Note: the word is now often overused for any disagreement — properly it means the deliberate undermining of someone’s sense of reality.
noun · /GAS-ly-ting/
Manipulating someone into doubting their own memory, perception, or sanity.
What it names
A specific, corrosive tactic — not just lying, but making the other person distrust their grip on reality.
Example
"That never happened, you’re remembering it wrong" — said often enough about things that plainly did happen — is gaslighting.
Related idea
DARVO (deny, attack, reverse victim and offender) describes a common gaslighting script.