The term 'USED HENNA' can be summarized by the crossword solution 'DYED, ' which is a four-letter word. Henna is a dye made from the leaves of the henna plant, which is native to tropical and subtropical regions of Africa, Asia, and Australia. It has been used for centuries to dye skin, hair, fingernails, leather, and wool. Henna is also used in traditional body art, such as mehndi, which is a form of temporary tattooing.