What is kryptonite meaning?

Kryptonite is a fictional mineral found in the Superman comic book series. It is considered to be Superman's Achilles' heel, as it weakens him and makes him vulnerable. The origin of kryptonite is attributed to the destruction of Superman's home planet, Krypton, as it was created by the planet's superheated core. It is usually depicted as a green crystal, but in some versions, it is shown as being red or blue. Kryptonite has also been used as a metaphor for anything that brings down a person or organization.