Hannya no Men (The Mask of Hannya [female demon]) (般若の面)
Hannya no Men, also known as Hannyamen or simply Hannya, is a mask of a female demon representing 'the face of a woman harboring jealousy and resentment' used in Noh theater.
Originally, 'hannya' (prajñā in Sanskrit) is a Buddhist term. It is a word synonymous to its Chinese translation 'chie' (to appoint, determine, and establish; the meaning is a little different form the 'chie' [wisdom, innovation, creativity] used in everyday language). However, there is little connection between Hannya and Hannya no Men.
According to one theory, it is said that the mask was named so because it was made by a Buddhist monk named Hannyabo. Alternatively, it is also said that Hannya became the mask's name because when Aoi no ue (Lady Aoi) in "The Tale of Genji" was agonized by Rokujo no Miyasudokoro's jealousy and became possessed by her vengeful spirit, she read the Hannya-kyo Sutra (Perfection of Wisdom Sutra) to perform a mizuho (an esoteric rite) and conquered the vengeful spirit.
In modern Japan, where Hannya as a Buddhist term is no longer commonly used, 'Hannya' may be used to mean 'Hannya no Men,' and furthermore, as 'a woman harboring jealousy and resentment.'