Horsetail, whose botanical name is Equisetum, is a herb that belongs to the family Equisetaceae. The name has been derived from the Latin words equus, that means 'horse' and seta meaning ' bristle'. Hence this perennial got its name horsetail because it bears a close resemblance to a horse's tail. This is an ancient herb that grew around 270 million years ago and is related to the family of ferns. Some other common names for the horsetail herb are bottlebrush, scouring rush and mare's tail. There are around 15 species of horsetail and this extractis taken from the common horsetail species also known as Equisetum arvense.