'headcanon' is jargon within general fandom. The term refers to the application of imagination against the established canon of a body of fiction, to expand up

'headcanon' is jargon within general fandom. The term refers to the application of imagination against the established canon of a body of fiction, to expand upon that body of work. Example: - Superman being from Krypton is canon. - Superman not truly being the son of Jor-El, because his mom slept around, might be one fan's headcanon.