Its name has no connection with its nature. 'mazhi' means ink and 'thandu' means stem. This herb, very common in Kerala is used to clean slate in my childhood days. The stem of this plant contains a lot of water. When we go to school we will collect these mazhithandu to rub the slate. I don't know if there is any other usage for this plant.
But my children doesn't know its name because they are using pen and pencil instead of slate and kallupencil. Its special smell always remember me of the primary school days and my innocent friends.