In English, name Siobhan means – Variant of Joan: God is gracious. Feminine form of John Famous Bearers: Legendary Pope Joan, who was a woman masquerading as a man; French heroine Joan of Arc (Jeanne dArc); actresses Joan Crawford, Joan Fontaine, and Joan Collins.. Other origins for name Siobhan include – English, Irish, Irish, Hebrew. Name Siobhan is most often used as a girl name or female name.