Key work on the traditional ballad was undertaken in the late 19th century in Denmark by Svend Grundtvig and for England and Scotland by the Harvard professor Francis James Child. They attempted to record and classify all the known ballads and variants in their chosen regions.
Gaslighting is a form of manipulation that seeks to sow seeds of doubt in a targeted individual or members of a group, hoping to make targets question their own memory, perception, and sanity. Using persistent denial, misdirection, contradiction, and lying, it attempts to destabilize the target and delegitimize the target's belief.
If you've never heard the term, prepare to learn it and live with it every day. Unless Trump starts behaving in a radically different way after he becomes President, gaslighting will become one of the words of 2017. The term comes from the 1930s play Gas Light and the 1940s Hollywood movie version in which a manipulative husband tries to unmoor his wife, played by Ingrid Bergman, by tampering with her perception of reality.