The term gaslighting someone means to manipulate someone.
Gaslighting is a form of psychological manipulation in which a person seeks to sow seeds of doubt in a targeted individual or in members of a targeted group, making them question their own memory, perception, and sanity.
It's called Gaslighting because the term gaslighting 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.
So that's where gaslighting comes from and how it got it's name gaslighting.