Siobhan originates in Hebrew language and means "God is merciful". It is an Irish form of the name Joan, a feminine form of John. In the 20th century, Siobhan was probably popularized by the Irish actress, Siobhan McKenna. Joan is a feminine form of John and as a female name has been used since the 17th century. One of the most famous bearers of this name was Joan of Arc, Maid of Orleans, a French heroine who led the French army in the Hundred Years' War. She was burned by the English at the stake for heresy and later on declared a martyr.