What is the origin of the term "gaslighting"?

The term "gaslighting" was first coined in a 1938 stage play entitled "Gas Light", set in the Victorian era, written by the British novelist and playwright Patrick Hamilton. In the play a young woman's husband slowly manipulates her into believing she is descending into insanity so that he can steal from her. It later became a British film in 1940 and then a Hollywood remake in 1944, starring Ingrid Bergman and Angela Lansbury in her debut role.

It has become the term used to describe a form of emotional abuse and coercive control, loosely defined as making someone question their own reality.

The term may also be applied to a person (a "gaslighter") who presents a false narrative to another group or person which leads them to doubt their perceptions and become misled (generally for the gaslighter's own benefit), disoriented or distressed. Generally, this dynamic is possible only when the audience is vulnerable, such as in unequal power relationships, or when the audience is fearful of the losses associated with challenging the false narrative. Gaslighting is not necessarily malicious or intentional, although in some cases it is.