The word Mehendi - or Mehndi - the art of henna and/or turmeric painting or tattoo, is derived from the Sanskrit word
mendhikā, which means Henna.
The use of mehendi is described in the earliest Hindu Vedic ritual books. It was originally used for women's palms, and sometimes for men. Mehendi (staining oneself with henna paste) is a Vedic custom intended to emphasize the existence of an inner sun through external artistic representation.
Learn more about henna
here.