The first time I heard the word "gaslighting" was in the early 00s when Richard Hillman in Corrie tricked his mother in law into believing she had dementia. I think the meaning used to be quite specific and usually in domestic abuse cases, where the abuser tries to make the person doubt their own reality. It's been used way more often in recent years, particularly when Boris Johnson was PM it seemed people had started to use it just to mean "lying". Even more recently, online I've seen other people accuse others of gaslighting when all they're doing really is disagreeing, not even lying! AIBU to think the meaning of the word has been hopelessly diluted?